Chemistry & Materials Science

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304 domain-specific abstractions whose origin domain is Chemistry & Materials Science. They span 275 subdomains — sort by that column to group them, or click any subdomain to filter to it.

Abstraction	Subdomain	Description
Accelerated solvent extraction	Analytical ChemistrySample Preparation	Accelerated solvent extraction (ASE), also known as pressurized solvent extraction (PSE), is a method for extracting various chemicals from a complex solid or semisolid sample matrix.
Acid Salt	Inorganic Salts and Acid Base Nomenclature	Classify a salt as an acid salt when its anion retains replaceable acidic hydrogen after partial deprotonation of a polyprotic parent acid, independently of whether its aqueous solution has pH below 7.
Acidic	Acid Base Chemistry	Having acid character under a stated chemical frame, such as proton donation, electron-pair acceptance, or medium hydronating ability.
Acidity function	Physical Organic ChemistryAcid Base Scales in Concentrated Media	Measure a solvent system's effective hydron-donating or accepting power relative to a specified indicator family when ordinary dilute-aqueous pH is not an adequate standalone scale.
Acoustic emission	Materials Science	Transient elastic waves released within a solid by rapid irreversible changes such as crack growth, plastic deformation, or phase transformation.
Action Spectroscopy	SpectroscopyPhotochemistry	Record a light-triggered product or response across excitation wavelengths instead of measuring only how much light a specimen absorbs.
Adsorption	Surface Science	Molecules partition out of a bulk fluid to concentrate on a solid surface bearing a finite population of binding sites, producing a saturating relationship between bulk concentration and surface loading captured by an adsorption isotherm.
Adsorption Isotherm	Surface Chemistry	At fixed temperature, trace how much adsorbate accumulates on a solid surface against its bulk concentration, then fit the curve to a functional form whose shape both extracts the surface's capacity and affinity and tests whether its sites are uniform, heterogeneous, or multilayer.
Aerobic Respiration	BiochemistryCellular Bioenergetics	A membrane-coupled metabolic process that transfers electrons from reduced biological fuels through a respiratory chain to molecular oxygen, captures redox energy as an electrochemical gradient, and uses that gradient to synthesize ATP.
Affinity electrophoresis	Biochemical AnalysisElectrophoretic Binding Assays	Detect or quantify biospecific binding by allowing complex formation during electrophoresis to alter a molecule’s mobility, band pattern, or migration boundary.
Aggregation-induced emission	Photophysical Chemistry	Enhanced light emission by certain luminophores when molecular aggregation restricts nonradiative motions that quench fluorescence in dilute solution.
Agostic interaction	Organometallic Chemistry	A three-center interaction in which a ligand C–H bond donates electron density to a nearby coordinatively unsaturated transition-metal center.
Amphiphile	Colloids and Interfaces	An amphiphile couples solvent-affine and solvent-averse regions in one unit, enabling condition-dependent interfacial organization or self-assembly.
Analysis of Water Chemistry	Analytical ChemistryWater Analysis	The purpose-driven sampling, preservation, measurement, quality control, and interpretation of chemical constituents and properties in water to support water-quality, treatment, process, pollution, hydrologic, or geochemical decisions.
Analytical Method	Analytical ChemistryMethod Validation	A repeatable and reviewable procedure that selects inputs, applies explicit transformations or interpretive rules, and produces findings about a defined question under stated assumptions and quality controls.
Analytical technique	Analytical Chemistry	A defined chemical-measurement procedure that prepares a material, produces a selective response to composition, calibrates that response, and identifies or quantifies target components with stated uncertainty and interference limits.
Analytical thermal desorption	Analytical ChemistryGas Chromatography	An analytical technique that traps volatile compounds on a sorbent and thermally releases them as a concentrated, narrow-band gas-chromatography sample.
Applied spectroscopy	Analytical Spectroscopy	The practical use of a spectrally resolved sample response, interpreted through method-specific physics, reference signatures, or calibration, to identify, characterize, or quantify elements, compounds, concentrations, or material states.
Arrow Pushing	Reaction MechanismsOrganic Chemistry	Use curved arrows to specify a local formal reassignment of electrons in a chemical structural drawing.
Atom-Bond Connectivity Index	Chemical Graph TheoryMolecular Topological Indices	A degree-based graph descriptor that sums √[(d(u)+d(v)−2)/(d(u)d(v))] once over every edge to produce a label-independent scalar.
Atomic Absorption Spectroscopy	Analytical ChemistryAtomic Spectrometry	An elemental-analysis method that converts an analyte into free ground-state atoms, measures attenuation of element-selective resonance radiation, and infers concentration through matrix-appropriate calibration and interference control.
Atomic Spectroscopy	Analytical Chemistry	Atomic spectroscopy uses element-specific atomic absorption, emission, fluorescence, or related spectra to identify and quantify elemental composition.
Atoms in molecules	Quantum ChemistryTheoretical Chemistry	The quantum theory of atoms in molecules, which partitions electron density into atomic basins bounded by zero-flux surfaces and reads density critical points and gradient paths as a topology of molecular structure.
Ball-on-ring test	Materials ScienceBiaxial Strength Testing of Brittle Disks	Estimate the biaxial flexural strength of a brittle disk by loading its central region against annular support so the critical tensile field lies away from edge flaws, with stress inferred through a declared mechanics model.
Bauschinger effect	Materials ScienceMetal Plasticity	The Bauschinger effect refers to a property of materials where the material's stress/strain characteristics change as a result of the microscopic stress distribution of the material.
Bent bond	Organic ChemistryChemical Bonding	A strained small-ring carbon–carbon bond described by off-axis bonding character, whose orbital or computed-density shape depends on the molecule and model.
Bent's rule	Chemical Bonding and Molecular Structure	The valence-bond heuristic that a central atom directs hybrid orbitals with more s character toward electropositive substituents and more p character toward electronegative substituents.
Bipolar Electrochemistry	Electrochemistry	Bipolar electrochemistry is a phenomenon in electrochemistry based on the polarization of conducting objects in electric fields.
Boltzmann–Matano Analysis	Diffusion Analysis	Infer concentration-dependent interdiffusivity from a diffusion-couple profile using a mass-balanced reference plane.
Bond Valence Method	Coordination ChemistryCrystallography	Bond Valence Method is a recurring coordination chemistry, crystallography identity in which empirical bond-valence contributions are summed around an atom to estimate oxidation state and validate localized-bond structures.
Born–Mayer equation	Solid State Chemistry	A lattice-energy equation for ionic crystals that combines Coulomb attraction with an exponential short-range repulsion approximated through a characteristic range parameter.
Bradford Protein Assay	BiochemistryProtein Quantification	A colorimetric concentration assay in which protein binding stabilizes the blue form of Coomassie Brilliant Blue G-250 and absorbance near 595 nm is interpreted against a matched standard curve.
Brønsted–Lowry Acid–Base Theory	Physical ChemistryAcid Base Chemistry	A proton-transfer framework that assigns acid and base roles to interacting species and relates each to its conjugate partner.
Buffer Solution	Acid Base ChemistrySolution Chemistry	A solution containing an acid-base conjugate system or equivalent reservoir that limits pH change under modest acid or base addition within a finite capacity and stated conditions.
Calorimetry	ThermochemistryPhysical Chemistry	Inferring heat transfer from measured changes in a calibrated system and its surroundings.
Capillary Electrochromatography	Analytical ChemistryCapillary Separations	A capillary separation method in which high voltage drives electroosmotic flow through a chromatographic stationary phase and analytes separate through combined electrophoretic mobility and partitioning.
Capped Octahedral Molecular Geometry	Coordination Chemistry	Describe a seven-coordinate center as six ligand positions forming an octahedral core plus a seventh position capping one triangular face, with idealized C3v symmetry and measurable distortions.
Capped Trigonal Prismatic Molecular Geometry	Coordination ChemistryStereochemistry	A seven-coordinate molecular shape consisting of a central atom, six ligands forming a trigonal prism, and a seventh capping one rectangular face, ideally with C2v symmetry.
Carbonation (Chemistry)	Carbonate Chemistry	This carbonate-system branch of chemical carbonation reacts CO2 with water or a basic partner to form carbonic acid, bicarbonate, or carbonate; medium controls the product and consequence.
Catalytic cycle	CatalysisReaction Mechanisms	In chemistry, a catalytic cycle is a multistep reaction mechanism that involves a catalyst.
Catalytic resonance theory	CatalysisDynamic Catalyst Theory	A catalysis theory predicting rate enhancement when a catalyst's binding energetics are modulated at frequencies commensurate with the characteristic kinetics of adsorption, surface reaction and desorption.
Ceiling Temperature	Polymer ChemistryPolymer Thermodynamics	The condition-dependent temperature above which a given reversible chain polymerization does not form high-molar-mass polymer.
Cerimetry	Analytical ChemistryRedox Titration	Cerimetry or cerimetric titration, also known as cerate oximetry, is a method of volumetric chemical analysis developed by Ion Atanasiu.
Characteristic Property	Substance Characterization	Use a physical or chemical property whose value is independent of sample amount under declared conditions as reproducible evidence for distinguishing or classifying substances.
CHELPG	Computational ChemistryPartial Charge Models	A grid-based electrostatic-potential fitting method that assigns atom-centered partial charges so their Coulomb potential approximates a computed molecular electrostatic potential.
Chemical Bond	Chemical BondsQuantum ChemistryChemical Structure	A chemical bond is a stabilizing association among atoms or ions within a molecule, crystal, metal, or other chemical structure, arising from quantum-mechanical and electrostatic organization of nuclei and electrons and characterized by energy, distance, directionality, order, and electron distribution.
Chemical formula	Chemical Notation	A symbolic notation specifying the elemental composition and, depending on formula type, ratios, atom counts, connectivity, charge or structural arrangement of a chemical substance.
Chemical Process	Chemical ReactionsChemical Processes	A temporally or spatially organized transformation in which substances undergo a change in chemical identity through reaction under declared physical and chemical conditions.
Chemical space	CheminformaticsMolecular Representation	The conceptual set of chemically admissible molecules under declared construction rules, represented by coordinates or descriptors that permit comparison, search and coverage analysis.
Chemical trap	Physical Organic ChemistryReaction Mechanisms	A reagent-based method for detecting a fleeting chemical species through a more characterizable reaction product.
Cis effect	Organometallic ChemistryCoordination Chemistry	The selective labilization of a carbonyl ligand cis to another ligand in an octahedral metal-carbonyl complex, arising from coupled electronic and steric influences.
Cis–Trans Isomerism	Stereochemistry	A pairwise stereochemical relation between fixed-constitution configurations whose designated groups occupy geometry-specific same-side or opposite positions.
Citric acid cycle	Biochemistry	A cyclic metabolic pathway that oxidizes acetyl units, regenerates oxaloacetate and transfers reducing equivalents for cellular energy metabolism.
Clar's rule	Physical Organic ChemistryAromaticity	In organic and physical organic chemistry, Clar's rule is an empirical rule that relates the chemical stability of a molecule to its aromaticity.
Clathrate Compound	Inclusion Compounds	A guest-containing inclusion compound whose host molecule or host-molecule arrangement forms a cage enclosing a guest molecule.
Colligative Properties	Solution Thermodynamics	A class of solution-property shifts whose ideal dilute limiting behavior depends on dissolved-particle loading rather than solute identity.
Collision frequency	Chemical Kinetics	The expected number of encounters between specified atomic or molecular species per unit volume and unit time under a kinetic model.
Conia–Ene Reaction	Organic Synthesis	An intramolecular carbon–carbon bond-forming cyclization in which an enolizable carbonyl partner reacts with a tethered alkene or alkyne, thermally or through catalytic activation, to form a ring.
Conjugated System	Physical Organic Chemistry	A bonded molecular segment whose adjacent compatible orbitals interact across intervening sigma bonds to form a coupled electronic path.
Constraint (Computational Chemistry)	Computational ChemistryConstrained Molecular Dynamics	An explicitly enforced restriction on molecular coordinates or collective variables during optimization or dynamics, defining an admissible configuration manifold and associated reaction forces.
Continuous Cooling Transformation	Physical MetallurgySteel Phase Transformation Kinetics	A material-specific time–temperature map that overlays continuously decreasing thermal paths on transformation-start, fraction, finish, and martensite boundaries to predict which microstructural products form during practical cooling from a parent phase.
Coprecipitation	Analytical ChemistryPrecipitation Chemistry	In chemistry, coprecipitation (CPT) or co-precipitation is the carrying down by a precipitate of substances normally soluble under the conditions employed.
Corey–Pauling rules	Structural ChemistryProtein Structure	In biochemistry, the Corey–Pauling rules are a set of three basic statements that govern the secondary nature of proteins, in particular, the CO-NH peptide link.
COSMO solvation model	Computational SolvationQuantum Chemistry	A continuum-solvation model that estimates solute–solvent electrostatics by scaling conductor-limit polarization charges on a segmented molecular cavity for a finite dielectric solvent.
Critical relative humidity	Materials StorageHygroscopic Materials	Critical relative humidity denotes property of water-soluble substances within materials storage.
Crossed molecular beam	Chemical PhysicsReaction Dynamics	In analytical chemistry, crossed molecular beam experiments involve two beams of atoms or molecules which are collided together to study the dynamics of the chemical reaction, and can detect individual reactive collisions.
Crystal Field Theory	Inorganic Chemistry	Crystal field theory models electrostatic splitting of a metal ion's orbital levels by its local coordination environment to interpret spin and spectra.
Crystal Lattice	Solid State Structure	The infinite, translationally periodic arrangement of a crystalline solid — a few-atom unit cell tiled by three lattice vectors — whose symmetry, drawn from a finite catalog of space groups, deductively fixes which physical properties are allowed and which forbidden.
Crystal structure prediction	Computational Materials ScienceSolid Structure Search	Computational search for thermodynamically or kinetically plausible crystal arrangements from composition or molecular identity by exploring periodic structures and ranking their energies or free energies.
Crystallization	Materials ScienceCrystal Formation	A parent phase is driven into conditions where an ordered solid can form, stable crystalline nuclei appear or are supplied, and interfacial growth converts mobile building units into a crystal population whose number, size, form, and purity record the competition among thermodynamics, transport, and kinetics.
Crystallographic Disorder	Structure Refinement	Crystallographic disorder is variation in atomic identity or position around a crystal's average repeating structure.
D-block contraction	Inorganic Chemistry	The smaller-than-expected atomic radii of period-four p-block elements caused by incomplete shielding from filled 3d electrons.
Dangling bond	Solid State ChemistrySurface Chemistry	In chemistry, a dangling bond is an unsatisfied valence on an immobilized atom.
Davies equation	Solution Thermodynamics and Electrochemistry	An empirical extension of Debye–Hückel theory that estimates electrolyte activity coefficients from ionic strength by adding a fitted finite-concentration correction.
Determination of equilibrium constants	Physical ChemistryAnalytical Chemistry	Equilibrium constants are determined in order to quantify chemical equilibria.
Dewetting	Interfacial ScienceThin Films	The withdrawal and breakup of a film from a substrate or adjoining phase as interfacial energetics favor reduced coverage over continued wetting.
Die Swell	Polymer Processing	The transverse expansion of an extruded stream after it leaves a constraining die.
Differential Scanning Calorimetry	Analytical ChemistryThermal Analysis	A thermoanalytical measurement that scans a sample and reference through a controlled temperature program and records differential heat flow or power, revealing heat capacity changes and thermal transitions.
DIIS	Computational Quantum ChemistrySelf Consistent Field Methods	DIIS (direct inversion in the iterative subspace or direct inversion of the iterative subspace), also known as Pulay mixing, is a technique for extrapolating the solution to a set of linear equations by directly minimizing an error residual (e.g. a Newton–Raphson step size) with respect to a linear combination of known sample vectors.
Dilution	Solution Chemistry	Dilution is the process of decreasing the concentration of a solute in a solution, usually simply by mixing with more solvent like adding more water to the solution.
Directional Solidification	Solidification Processing	Advance a liquid-to-solid transformation through material along a preferred direction maintained by a spatial thermal gradient.
Dislocation	Line Defect Enabling Deformation	A one-dimensional line defect in a crystal that carries plastic deformation by sweeping across a slip plane one atomic row at a time, letting a metal yield at stresses two to four orders of magnitude below what shearing the whole lattice at once would require.
Dislocation Creep	Crystal Plasticity	Dislocation creep is sustained crystal deformation carried by moving and interacting dislocations, whose obstacles, mobility and flow law depend on material and stress–temperature regime.
Dissociation (chemistry)	Physical ChemistryChemical Equilibrium	Dissociation in chemistry is a general process in which molecules (or ionic compounds such as salts, or complexes) separate or split into other things such as atoms, ions, or radicals, usually in a reversible manner.
Distillation	Chemical EngineeringVapor Liquid Separation	A separation process that selectively vaporizes and condenses components of a liquid mixture according to volatility differences.
Double Bond Rule	Main Group Bonding	A historical main-group bonding heuristic expects conventional pi bonds to be less favored for heavier elements than for second-period analogues, while allowing documented exceptions.
Duhem–Margules equation	Solution Thermodynamics	A binary-mixture thermodynamic constraint equating composition-scaled changes in the components’ equilibrium partial vapor pressures.
Dukhin Number	Electrokinetics	A dimensionless electrokinetic ratio comparing conduction along a charged interface with conduction through its surrounding electrolyte.
Dunathan Stereoelectronic Hypothesis	Bioorganic ChemistryReaction Specificity in Pyridoxal Phosphate Dependent Enzymes	PLP-dependent enzymes select the primary bond broken at a substrate's alpha carbon by holding that sigma bond approximately perpendicular to the PLP–external-aldimine plane, aligning it with the conjugated p orbitals that stabilize developing carbanionic character.
Dynamic electrophoretic mobility	Colloid ScienceElectroacoustics	Dynamic electrophoretic mobility is a parameter that determines intensity of electroacoustic phenomena, such as Colloid Vibration Current and Electric Sonic Amplitude in colloids.
Electrochromatography	Separation ScienceAnalytical Chemistry	Electrochromatography is a chemical separation technique in analytical chemistry, biochemistry and molecular biology used to resolve and separate mostly large biomolecules such as proteins.
Electron backscatter diffraction	Materials CharacterizationElectron MicroscopyCrystallography	A scanning-electron-microscopy technique that records Kikuchi diffraction patterns from a highly tilted crystalline specimen and indexes band geometry to map crystal phase, orientation, boundaries, strain proxies, and texture at spatial resolution set by beam, material, preparation, and acquisition conditions.
Electrotyping	ElectrodepositionElectrometallurgy	A metal-copying method that deposits a shaped metal shell from a model's surface, historically used for printing plates and decorative reproductions.
ELISA	ImmunochemistrySolid Phase Enzyme Immunoassay	A heterogeneous solid-phase immunoassay that retains an antigen–antibody complex through washing and converts an enzyme-linked reporter’s substrate reaction into a controlled qualitative or quantitative measure of the target.
Empirical formula	Composition Notation	A chemical formula giving the simplest whole-number ratio of elements in a compound without specifying molecular atom count, connectivity or structure.
Empirical valence bond	Computational Chemistry	A calibrated multistate Hamiltonian method for approximating condensed-phase reaction free-energy surfaces.
Enantiomorph	CrystallographyStereochemistry	A pair of mirror-image forms that share shape but cannot be superposed using the allowed orientation-preserving motions of the stated space.
Endothermic Process	ThermochemistryPhysical Chemistry	A physical or chemical process that absorbs heat from its surroundings under the stated boundary conditions, giving the system a positive heat input and, at constant pressure, a positive enthalpy change.
Energy minimization	Computational ChemistryPotential Energy Surface MethodsMolecular Modeling	Computational search for an atomic arrangement that is a local or global minimum of a specified modeled potential energy under declared constraints.
Enthalpy of Neutralization	ThermochemistryAcid Base Chemistry	The enthalpy change of an acid–base neutralization, usually normalized per mole of water formed under specified conditions.
Enthalpy of reaction	Thermochemistry	The enthalpy change associated with a chemical reaction as written, equal under specified conditions to the stoichiometric sum of product enthalpies minus that of reactants, with the standard value referring to defined standard states.
Entropy of Activation	Chemical Kinetics	The model- and standard-state-qualified entropy change for forming an activated complex from reactants in a specified transition-state-theory kinetic step.
Ergun equation	Chemical EngineeringPacked Bed Flow	Estimate pressure loss through a packed bed by combining viscous and inertial terms scaled by fluid properties, particle size, void fraction, and superficial velocity.
Eshelby's inclusion	MicromechanicsMaterials Science	The classical micromechanics problem of an ellipsoidal region with prescribed eigenstrain constrained inside an infinite linear-elastic matrix, producing a uniform interior strain related by the Eshelby tensor.
Eutectic Mixture	Phase EquilibriaPhysical Chemistry	A eutectic system or eutectic mixture ( ) is a type of a homogeneous mixture that has a melting point lower than those of the constituents.
Exergonic process	Chemical Thermodynamics	A process whose Gibbs free-energy change is negative under declared temperature, pressure, composition, and state conventions, making the forward change thermodynamically favorable.
Explosive Boiling	Physical ChemistryPhase Transitions	In physical chemistry, explosive boiling or phase explosion is a process in which a superheated metastable liquid undergoes an explosive liquid–vapour phase transition into a stable two-phase state because of a massive homogeneous nucleation of vapour bubbles.
Eötvös rule	Physical Chemistry	An empirical corresponding-states relation approximating how a pure liquid’s surface tension decreases toward zero near its critical temperature.
FFC Cambridge Process	Extractive MetallurgyElectrochemistry	A molten-salt electrochemical reduction method that converts a solid metal oxide cathode directly toward metal by removing oxygen ions through a calcium-chloride electrolyte.
Fill power	Textile TestingDown Insulation	Fill power is a measure of the loft or "fluffiness" of a down product that is loosely related to the insulating value of the down.
Fire Point	Flammability TestingPetroleum TestingCombustion Science	The lowest temperature at which a liquid fuel's vapour continues burning for a specified duration after standardized ignition, measured by a defined fire-point test and distinct from flash point and autoignition temperature.
Flocculation	Colloid Science	Join dispersed particles or cells in a fluid into persistent multiunit flocs through contact and context-specific adhesion.
Flory–Huggins Solution Theory	Polymer PhysicsPolymer Solution Thermodynamics	A lattice theory of polymer–solvent mixing that combines size-corrected configurational entropy with an interaction parameter in the Gibbs free energy.
Fractional coordinates	Crystallography	Crystal coordinates expressing a point as coefficients of the unit-cell lattice basis.
Fractional crystallization (chemistry)	Separation ProcessesCrystallization	A staged separation in which components crystallize preferentially as temperature or composition changes, allowing purified solid fractions to be removed from a multicomponent liquid.
Fragment-Based Lead Discovery	Medicinal ChemistryLead Discovery	A drug-discovery strategy that validates weak binding by small fragments and grows, links, or merges them into higher-affinity lead candidates under structural and developability constraints.
Frank–Read Source	Crystal PlasticityLine Defect Dynamics	A pinned line defect that repeatedly bows under sufficient drive, sheds a closed defect loop, and retains its anchored segment for another emission cycle.
Free-Radical Addition	Reaction MechanismsRadical Chemistry	An elementary chemical step in which a radical bonds to an unsaturated substrate and leaves radical character on the resulting adduct.
Freezing-point depression	Solution Thermodynamics	The lowering of a solvent’s equilibrium freezing temperature caused by dissolved solute or mixing with another component.
Frustrated Lewis Pair	Main Group ChemistryCatalysis	A Lewis acid and Lewis base prevented by steric or geometric incompatibility from forming their usual stable adduct, leaving complementary reactivity available to cooperatively activate substrates such as hydrogen.
Fukui function	Conceptual Density Functional TheoryComputational Chemistry	Fukui function denotes function in computational chemistry within conceptual density-functional theory.
Fundamental Resolution Equation	Column Chromatography	An approximate chromatographic relation that separates pairwise peak resolution into plate-efficiency, selectivity and retention factors under fixed-condition assumptions.
Förster Resonance Energy Transfer	Physical ChemistryMolecular Spectroscopy	Nonradiative dipole-coupled transfer of excitation from a donor to a nearby acceptor chromophore, strongly dependent on separation.
Gas Electron Diffraction	Gas Phase Structural ChemistryStructural Chemistry	A method for determining gas-phase molecular geometry by scattering electrons from randomly oriented molecules and fitting a structural model to the corrected interference pattern.
Generalized valence bond	Quantum ChemistryValence Bond Theory	The generalized valence bond (GVB) is a method in valence bond theory that uses flexible orbitals in the general way used by modern valence bond theory.
Gent hyperelastic model	Polymer PhysicsRubber ElasticityHyperelasticity	The Gent hyperelastic material model is a phenomenological model of rubber elasticity that is based on the concept of limiting chain extensibility.
Geometric Phase Analysis	Electron MicroscopyQuantitative High Resolution Image Analysis	Recover local crystallographic displacement and strain from a periodic high-resolution electron-microscopy image by isolating reciprocal-lattice components and interpreting their spatial phase relative to a reference lattice.
Glass formation	Materials Physics	The kinetic arrest of a liquid or disordered material into an amorphous solid before crystallization can establish long-range order.
Grotthuss Mechanism	Physical ChemistryAqueous Proton Transport	Excess protonic charge advances through a connected hydrogen-bonded medium by local proton transfer and bond-network rearrangement, rather than solely by movement of one intact carrier.
Half-Reaction	Electrochemistry	A balanced, electron-explicit chemical equation representing one oxidation or reduction component of a redox process.
Harpoon Reaction	Reaction DynamicsElectron Transfer	A neutral-reactant reaction mechanism in which long-range electron transfer creates an ion pair whose attraction draws the partners closer before subsequent chemistry.
Helix–Coil Transition Model	Polymer Physical ChemistryBiophysical Chemistry	A statistical-mechanical model of a linear polymer as helix and coil states with distinct nucleation and propagation weights for cooperative conformational change.
Hofmeister Series	Physical ChemistryIon Specific Solution Effects	An empirical ordering of salts or ions by their effects on protein solubility and related solution properties.
Homologous Series	Chemical Classification and Structure Property Comparison	An indexed family of chemical species whose members preserve a declared structural motif while successive homologues differ by one fixed compositional or structural increment.
Hydrofunctionalization	Organic SynthesisAddition Reactions	A chemical addition family that places hydrogen and a distinct functional fragment across a carbon-containing unsaturated bond.
Hydrogen Bond	Intermolecular and Intramolecular Interactions	An evidence-supported attractive X–H···Y interaction in which a polarized, covalently bound hydrogen couples a donor fragment to an acceptor site with characteristic directionality and electronic response.
Hydrogen-Atom Abstraction	Reaction Mechanisms	An elementary chemical step in which an acceptor takes a hydrogen-atom equivalent from a donor bond, changing both bonds and donor-side radical character.
Hydrogen-Bond-Donor Catalysis	OrganocatalysisNoncovalent Catalysis	A molecular catalytic mode in which a regenerating hydrogen-bond donor interacts consequentially with a reacting species, changing the accessibility or selectivity of a reaction pathway.
Hydrogenography	Combinatorial Materials ScienceHydrogen Storage Materials	Hydrogenography is a combinatorial method based on the observation of optical changes on the metal surface by hydrogen absorption.
Hyper-Wiener Index	Chemical Graph Theory	Compress a connected molecular graph's shortest-path distance distribution into a scalar by summing both distance and squared distance over unordered vertex pairs.
Hypsochromic shift	Spectroscopy	A displacement of an absorption or emission band toward shorter wavelength and therefore higher frequency or photon energy.
Immunoassay	Analytical ChemistryBioanalytical ChemistryImmunochemistry	A biochemical analytical procedure that uses specific antibody–antigen recognition to convert the presence or amount of an analyte into an interpretable qualitative or quantitative signal.
Impulse excitation technique	Materials Testing	A nondestructive materials-characterization method that infers elastic moduli and damping from the resonant response of a lightly supported specimen after a small mechanical impulse.
Indentation Hardness	Mechanical TestingHardness Metrology	A method-dependent hardness measure relates a controlled indenter and load to a material's local impression or penetration response.
Indentation Size Effect	Materials ScienceInstrumented Indentation	The systematic dependence of indentation hardness or strength on contact size, depth, or load, often producing higher apparent hardness at smaller scales under controlled measurement.
Inert-pair effect	Inorganic ChemistryHeavy P Block Oxidation States	The increasing stability of oxidation states two below the group valence among heavier p-block elements because the outermost ns² electron pair participates less readily in bonding, with relativistic and shielding effects contributing.
Internal Standard	Analytical ChemistryCalibration	A quantitative calibration method that adds a fixed known amount of a distinct reference to every sample and calibrator and uses analyte-to-reference response ratios to cancel shared variation.
Intersystem Crossing	PhotochemistryMolecular Photophysics	A radiationless transition between electronic states of different spin multiplicity within a molecular system.
Intramolecular vibrational energy redistribution	Chemical Dynamics and Molecular Spectroscopy	The transfer of vibrational excitation among coupled modes within an isolated or weakly interacting molecule after energy is initially localized in particular quantum states.
Isotope Effect on Lipid Peroxidation	BiochemistryLipid PeroxidationFree Radical Chemistry	Reduced radical-chain lipid oxidation caused by deuterium substitution at hydrogen-abstraction sites in polyunsaturated lipids, established through matched kinetic comparison.
Isotopic labeling	Biochemical TracingRadiochemistry	Isotopic labeling (or isotopic labelling) is a technique used to track the passage of an isotope (an atom with a detectable variation in neutron count) through chemical reaction, metabolic pathway, or a biological cell.
Isovalent Hybridization	Quantum ChemistryChemical Bonding	In chemistry, isovalent or second order hybridization is an extension of orbital hybridization, the mixing of atomic orbitals into hybrid orbitals which can form chemical bonds, to include fractional numbers of atomic orbitals of each type (s, p, d).
Kapustinskii Equation	Inorganic ChemistrySolid State Chemistry	An approximate ionic-crystal lattice-energy formula based on ion count, charge product, radius sum, and an empirical distance correction.
Keeper (Chemistry)	Analytical Chemistry	Add a deliberately persistent compatible phase or surface during evaporative analytical sample preparation so the target analyte is less likely to volatilize, dry onto vessel walls, or become irrecoverable.
Kinetic capillary electrophoresis	Analytical ChemistryCapillary Electrophoresis	Kinetic capillary electrophoresis or KCE is capillary electrophoresis of molecules that interact during electrophoresis.
Kinetics	Reaction Kinetics	Describe how fast a chemical system moves among states by relating each species' rate of change to concentrations, temperature, and catalysts through rate laws — keeping the rate-and-path question separate from the thermodynamic endpoint the system is approaching.
Lamellar structure	Materials ScienceMicrostructures	A material microstructure made of fine alternating plate-like layers of distinct phases, commonly produced by coupled growth during eutectic or eutectoid transformations.
Laser Diffraction Analysis	Particle SizingLaser Scattering	Angular laser scattering from a dispersed particle population is inverted through an optical model into a volume-based equivalent-sphere size distribution.
Laser Flash Analysis	Materials ScienceThermal Property Metrology	A transient thermal-characterization method that infers a specimen's through-thickness thermal diffusivity from the time response of its rear surface after a short, spatially uniform energy pulse heats the front.
Law of reciprocal proportions	Historical Stoichiometric Laws	Relate the masses in which two elements separately combine with a fixed mass of a third to the mass ratio in which those two elements combine with each other, allowing a simple whole-number multiple.
LCP theory	Molecular GeometryInorganic Chemistry	The consistency of the interligand distances (F-F and O-F) in the above molecules is striking and this phenomenon is repeated across a wide range of molecules and forms the basis for LCP theory.
Ligand Binding Assay	BiochemistryBioassaysAnalytical Biochemistry	An analytical assay that infers ligand presence, quantity, or binding behavior from a detectable ligand–macromolecule binding interaction.
Linear molecular geometry	Molecular Geometry	Linear organic molecules, such as acetylene (), are often described by invoking sp orbital hybridization for their carbon centers.
Liquid-Phase Coalescence	Drop and Bubble Dynamics	Liquid-phase coalescence joins initially separate regions of the same liquid phase through an interfacial bridge after a separating film or gap fails.
Liquid–Liquid Extraction	Chemical Separation EngineeringSolvent Extraction and Liquid Liquid Distribution	Transfer selected dissolved species between contacting immiscible or partially miscible liquid phases, then disengage the phases as extract and raffinate, using equilibrium distribution, speciation control, and staging to obtain recovery and selectivity.
Machine-learned interatomic potential	Computational Materials ScienceAtomistic Simulation	A trained surrogate that maps atomic configurations to interatomic energy, and often forces, within a validated materials domain.
Magnetic circular dichroism	SpectroscopyPhysical ChemistryMagneto Optics	The magnetic-field-induced difference in absorption between left- and right-circularly polarized light propagating parallel to the field, used to resolve electronic transitions and magnetic sublevels.
Marcus Theory	Electron TransferPhysical Chemistry	Relate electron-transfer barriers to nuclear reorganization and reaction driving force, with rates interpreted under coupling and dynamical assumptions.
Mass concentration (chemistry)	Solution ChemistryConcentration Measures	Mass density of a component in a chemical mixture.
Mercury Intrusion Porosimetry	PorosimetryMaterials Characterization	Porosimetry is an analytical technique used to determine various quantifiable aspects of a material's porous structure, such as pore diameter, total pore volume, surface area, and bulk and absolute densities.
Mesomeric effect	Organic Chemistry	The persistent electron-density displacement a substituent produces through conjugated pi-bond or lone-pair resonance donation or withdrawal.
Metal aromaticity	Inorganic and Cluster Chemistry	The extension of aromaticity criteria to delocalized cyclic electron systems composed partly or wholly of metal atoms or metal–ligand orbitals.
Metal–Ligand Multiple Bond	Organometallic ChemistryInorganic Chemistry	A formal description of a metal–ligand interaction with substantial bonding beyond one sigma component, commonly involving ligand-to-metal or metal-to-ligand pi overlap and a conventionally assigned bond order above one.
Michaelis–Menten Kinetics	BiochemistryEnzyme Kinetics	An initial-rate enzyme-kinetics regime in which a variable substrate drives a rectangular-hyperbolic rate toward a limiting value V, with Km marking the substrate concentration at half that limit.
Mie potential	Molecular Modeling	A two-power pair potential combining short-range repulsion and longer-range attraction between particles.
Mixed Quantum–Classical Dynamics	Theoretical and Computational ChemistryNonadiabatic Molecular Dynamics	A family of nonadiabatic molecular-dynamics methods that propagates nuclei on classical trajectories, electronic states quantum mechanically, and couples the two descriptions through forces and state-transfer information.
Molar attenuation coefficient	SpectroscopyAnalytical Chemistry	A wavelength-dependent proportionality between a species' molar concentration–pathlength product and its absorbance, quantifying how strongly one mole-per-volume of that species attenuates light.
Molar Concentration	Physical ChemistryAnalytical Chemistry	The amount of a specified chemical species divided by the volume of the mixture containing it, conventionally expressed as moles per litre and dependent on temperature through volume.
Molar refractivity	Physical Chemistry	A molar optical-response quantity combining refractive index and density to estimate the electronic polarizability contributed by one mole of material.
Molar volume	Chemical MetrologyPhysical Chemistry	In chemistry and related fields, the molar volume, symbol V m , or \tilde V of a substance is the ratio of the volume (V) occupied by a substance to the amount of substance (n), usually at a given temperature and pressure.
Molecular formula	Chemical Nomenclature	A molecular formula represents a molecular substance by listing the chemical elements present and the number of atoms of each element in one molecule.
Molecular Geometry	Structural ChemistryStereochemistry	Molecular geometry is the three-dimensional arrangement of atomic nuclei in a molecule or molecular ion, described through connectivity, bond lengths, bond angles, dihedral angles, coordination, symmetry, and conformational or vibrational averaging.
Molecular Hamiltonian	Quantum Chemistry	The quantum operator representing the kinetic and Coulomb potential energies of a molecule's electrons and nuclei.
Molecularity	Chemical Kinetics	The number of reacting species participating in one elementary reaction step as written in its molecular mechanism.
Molecule mining	Cheminformatics	Molecule mining is the process of data mining, or extracting and discovering patterns, as applied to molecules.
Multiple antisymmetry	CrystallographySymmetry Theory	In crystallography and materials science multiple antisymmetry is the concept of a substance possessing two or more different types of antisymmetry simultaneously.
Multiple Bond	Chemical Bonding	In chemistry, bond order is a formal measure of the multiplicity of a covalent bond between two atoms.
Mutarotation	Stereochemistry	The time-dependent change in a solution's optical rotation as interconverting anomers approach equilibrium.
N-electron valence state perturbation theory	Quantum Chemistry	A multireference perturbation theory adding dynamic correlation to a complete-active-space reference.
Negative thermal expansion	Materials Physics	The material response in which length or volume decreases over a temperature interval as temperature increases.
Nephelauxetic effect	Coordination ChemistryElectronic Structure of Complexes	The reduction of interelectronic repulsion parameters when a transition-metal ion forms a complex, interpreted as expansion or delocalization of its d-electron cloud through covalent metal–ligand interaction.
Non-stoichiometric compound	Solid State ChemistryCrystal Defects	Non-stoichiometric compounds also exhibit special electrical or chemical properties because of the defects; for example, when atoms are missing, electrons can move through the solid more rapidly.
Normal Fault	Earth Sciences	A fracture in the crust where the hanging wall has dropped relative to the footwall along a plane dipping near 60°, whose hanging-wall-down dip-slip geometry is the diagnostic signature of horizontal extension in the crust.
Nuclear Reaction Analysis	Materials ScienceSurface AnalysisIon Beam Analysis	A materials-analysis method inferring selected elemental depth profiles from ion-induced nuclear-reaction signals.
Octahedral Molecular Geometry	Inorganic Chemistry	Arrange six directly attached atoms or donor positions around one center in octahedral directions.
Octane rating	Fuel ChemistryPetroleum Chemistry	An octane rating, or octane number, is a standard measure of a fuel's ability to withstand compression in an internal combustion engine without causing engine knocking.
Octet rule	Chemical Bonding Theory	A chemical heuristic that many main-group atoms form bonds so their valence shells attain eight electrons resembling a noble-gas configuration.
Orbital-Free Density Functional Theory	Computational ChemistryElectronic Structure Theory	In computational chemistry, orbital-free density functional theory (OFDFT) is a quantum mechanical approach to electronic structure determination which is based on functionals of the electronic density.
Orogenic Belt	Earth Sciences	Read a mountain range, its foreland basin, and its metamorphosed core as one datable record of a single sustained plate convergence — reconstruct the collision's direction, style, and timing from the belt's hinterland-to-foreland polarity and brittle-to-ductile depth gradient.
Osmosis	Membrane Transport	Osmosis is solvent transport across a selectively permeable barrier governed by a solvent chemical-potential difference and its pressure balance.
Ostwald Ripening	Physical Chemistry	Larger particles grow at the expense of smaller ones because higher surface curvature makes small particles more soluble (the Gibbs-Thomson effect), so material dissolves off them, diffuses through the matrix, and redeposits onto large ones — coarsening the population on a t^(1/3) law.
Oxidation state	Inorganic Chemistry	A formal electron-bookkeeping value assigned to an atom by treating each heteronuclear bond as fully ionic according to an electronegativity convention.
Oxygen reduction reaction	Electrochemistry and BioenergeticsElectrocatalysis	The electron-accepting half-reaction that reduces molecular oxygen to water, peroxide, or a medium-specific oxygen product.
Particle size distribution	Granulometry	A distribution specifying relative particle amount by size for a powder, granular solid, or dispersion.
Passivation	Corrosion Science	The phenomenon in which a reactive metal spontaneously grows a thin, dense oxide film from its own oxidation that throttles further corrosion by orders of magnitude — a self-limiting barrier that protects an underlying metal which remains thermodynamically unstable.
Pentagonal pyramidal molecular geometry	Coordination ChemistryMolecular Geometry	A six-coordinate geometry with five ligands forming a pentagonal base and one ligand at a single axial apex.
Periodic Trends	Periodic Properties	Infer recurring changes in elemental properties across periods and down groups by relating atomic number and electron configuration to effective nuclear charge, shell structure, shielding, and orbital occupancy.
Photodegradation	Photochemistry and Material AgingMaterials Science	Light-initiated chemical or structural deterioration of a material, with effects determined by its absorption and environment.
Photoemission orbital tomography	Surface ScienceAngle Resolved Photoemission and Orbital Imaging	Infer occupied surface-state or molecular-orbital structure by comparing angle-resolved photoemission momentum maps with Fourier-space orbital models and, under declared final-state assumptions, reconstructing real-space orbital information.
Piezooptic effect	Optical Materials	A change in a material's refractive index caused by applied mechanical pressure or stress.
Pinch analysis	Chemical EngineeringHeat Integration and Process Design	A thermodynamic design methodology that sets minimum hot and cold utility targets and restructures heat recovery around a pinch temperature constraint.
Plasma treatment (textiles)	Textile EngineeringSurface Modification	A textile-surface modification process in which a controlled low-temperature plasma cleans, activates, etches, cross-links, deposits, or grafts the outer fiber layer while largely preserving bulk material properties.
Pole figure	Materials Texture Analysis	A stereographic or equal-area projection showing the orientation distribution of selected crystallographic plane normals or directions relative to a specimen frame.
Polychromatic Symmetry	Color GroupsPeriodic and Quasiperiodic Patterns	Symmetry of a pattern with at least three color classes under compatible spatial operations and nontrivial global color permutations.
Polymerization	Macromolecular Chemistry	The process by which many small monomer units are covalently linked into long chains whose bulk properties emerge from the chain-length distribution rather than from any single monomer's chemistry — the chain, not the monomer, being the unit of analysis.
Pouillet Effect	Surface ChemistryHeat of Wetting	Heat associated with liquid wetting of a dry porous or divided solid, usually released as interfaces form.
Pourbaix diagram	Electrochemistry	A potential-versus-pH phase map showing thermodynamically predominant aqueous species and solid phases for a declared electrochemical system.
Powder diffraction	CrystallographyMaterials Characterization	Powder diffraction is a scientific technique using X-ray, neutron, or electron diffraction on powder or microcrystalline samples for structural characterization of materials.
Precession electron diffraction	Materials CharacterizationElectron Diffraction	A transmission-electron-microscopy diffraction method that rocks a tilted incident beam around the optic axis and de-rocks the outgoing pattern, integrating intensities over orientations to reduce dynamical artifacts.
Precipitation	Solution Chemistry	Separate a dissolved substance as a solid once its concentration is driven past the solvent's solubility limit and a nucleation pathway opens, turning a latent supersaturation into an abrupt, self-limiting phase change.
Principal interacting orbital	Quantum ChemistryBonding Analysis	A quantum-chemical analysis that resolves dominant interfragment interactions into interpretable, semi-localized orbital pairs.
Processing-Structure-Property Relationship	Materials Science Fundamentals	Explain a material's behavior by inserting a mandatory mediator — structure — between processing and properties, with one-way causal arrows so intervention enters only at the processing end and design reasons forward through the structure it reaches.
Pseudo-Jahn–Teller Effect	Theoretical Chemistry	A symmetry-lowering instability in a nondegenerate electronic state when nuclear motion couples it strongly enough to another state to overcome restoring stiffness.
Pyroelectricity	Materials Physics	The change in spontaneous electric polarization and resulting surface charge produced by a change in a material’s temperature.
Quasicrystal	CrystallographyMaterials Science	A crystalline material with long-range ordered, nonperiodic structure of the quasicrystal class.
Radical Disproportionation	Radical ChemistryOrganic Chemistry	The most thoroughly studied radical disproportionation reactions have been conducted with alkyl radicals, but there are many organic molecules that can exhibit more complex, multi-step disproportionation reactions.
Randić index	Chemical Graph Theory	A graph invariant summing the reciprocal square root of endpoint-degree products over all edges, widely used as a molecular connectivity descriptor.
Random coil	Polymer PhysicsPolymer Chemistry	A random coil is a polymer-chain conformational ensemble lacking stable long-range order, described statistically by many rapidly interconverting local configurations rather than one fixed structure.
Random graph theory of gelation	Polymer Network Modeling	A polymer-network theory representing multifunctional monomers and their bonds as random graphs so giant-component emergence marks the gel point.
Raoult's Law	Physical Chemistry	In an ideal liquid mixture, relates each component's equilibrium vapor partial pressure to its liquid mole fraction and pure-component vapor pressure.
Reaction Mechanism	Reaction MechanismsChemical Kinetics	An evidence-constrained chemical representation of the elementary-step sequence, intermediates, transition states, and bond changes proposed to produce an observed overall reaction.
Redox	ElectrochemistryRedox Chemistry	Redox ( , , reduction–oxidation or oxidation–reduction) is a type of chemical reaction in which the oxidation states of the reactants change.
Reducing agent	Redox Chemistry	In chemistry, a reducing agent (also known as a reductant, reducer, or electron donor) is a chemical species that "donates" an electron to an (called the , , , or ).
Reduction Potential	ElectrochemistryRedox Chemistry	A reference-relative electrode potential quantifying a redox couple's tendency to accept electrons under declared chemical and thermodynamic conditions.
Relative Atomic Mass	Atomic Weights and Isotopic Composition	The dimensionless ratio of an atom's or specified element sample's mean atomic mass to the atomic mass constant, with a sample value determined by its isotopic composition.
Relativistic quantum chemistry	Quantum ChemistryRelativistic Electronic Structure	Compute molecular and elemental electronic structure with Hamiltonians that incorporate special relativity, capturing scalar-relativistic and spin–orbit effects that grow important for heavy nuclei.
Rod group	Crystallography	One of the three-dimensional crystallographic line groups describing structures periodic along exactly one spatial direction.
Roothaan–Hall Equations	—	Express finite-basis Hartree–Fock stationarity as a nonlinear generalized eigenproblem FC = SCε whose Fock matrix must be rebuilt self-consistently from the occupied-orbital coefficients.
Rustproofing	Corrosion EngineeringSurface Protection	The prevention or delay of rust on iron or steel by protective treatment or design, with effectiveness conditioned by exposure, wear, and maintenance.
Salt Spray Test	Corrosion TestingMaterials Testing	The salt spray test (or salt fog test) is a standardized and popular corrosion test method, used to check corrosion resistance of materials and surface coatings.
Schenck Ene Reaction	Organic PhotochemistrySinglet Oxygen Ene Chemistry	Oxyfunctionalize an alkene bearing an allylic hydrogen by reacting it with singlet molecular oxygen, transferring that hydrogen and transposing the double bond to produce an allylic hydroperoxide whose selectivity and downstream handling remain explicit.
Scherrer Equation	X Ray Powder DiffractionCrystallite Size Line Broadening	A powder-diffraction size relation that converts specimen-caused Bragg-peak breadth into an apparent mean coherent-domain length through wavelength, diffraction angle, and a declared shape-and-breadth factor.
Schmidt double bond rule	Organic ChemistryReactivity Rules	The Schmidt double-bond rule states that a sigma bond attached to an atom adjacent to a double bond can display enhanced reactivity relative to an analogous bond attached directly to the double-bonded system.
Searching the conformational space for docking	Computational ChemistryMolecular Docking	Explore the astronomically large set of relative molecular poses and internal conformations with a bounded sampling strategy, then rank the sampled states for plausible binding arrangements.
Secondary electrospray ionization	Analytical Mass SpectrometryAmbient Ionization	Ionize neutral gas-phase or aerosol analytes through interaction with charged species generated by an electrospray, coupling an ambient sample stream to mass-spectrometric detection while keeping transfer and response biases explicit.
Selective Dealloying	Metallurgy	Selective dealloying preferentially removes one alloy constituent, leaving an enriched surface or reorganized residual network.
Semisynthesis	Organic SynthesisNatural Products	Build a target compound by chemically transforming a biologically supplied precursor that already carries part of its structure.
Short range order	CrystallographyMaterials ScienceAmorphous Solids	In crystallography, short range order refers to the regular and predictable arrangement (i.e. crystalline lattice) of atoms over a short distance, usually with one or two atom spacings.
Side Reaction	Process Chemistry	An alternative chemical transformation running in parallel with the desired one, competing for the same substrate through its own rate law, so that selectivity — the ratio of desired rate to the sum of all competing rates — governs yield rather than the desired reaction's absolute speed.
Silk surfacing	Textile Finishing	Silk surfacing was a surface finishing of cotton to obtain an appearance similar to silk.
Sintering	Powder Metallurgy	The thermally or pressure-assisted bonding of a particulate compact into a coherent solid through interparticle neck growth and microstructural transport without complete bulk melting.
Site-directed spin labeling	Epr SpectroscopyBiophysical Chemistry	A protein-structure and dynamics technique that engineers a chosen labeling site, covalently attaches a paramagnetic reporter, and interprets its electron-paramagnetic-resonance spectrum in the context of retained protein function.
Slater-type orbital	Quantum Chemistry	Slater-type orbitals (STOs) or Slater-type functions (STFs) are functions used as atomic orbitals in the linear combination of atomic orbitals molecular orbital method.
Slater–Condon rules	Quantum Chemistry	Rules reducing matrix elements of one- and two-body operators between Slater determinants to sums of one- and two-orbital integrals.
Soft independent modelling of class analogies	ChemometricsSupervised Classification	Soft independent modelling by class analogy (SIMCA) is a statistical method for supervised classification of data.
Solubility	Physical Chemistry	Specify the maximum amount of a solute that can dissolve in a solvent as a function of temperature, pressure, pH, and ionic strength — the equilibrium point where dissolved and undissolved chemical potentials equalize and net transfer ceases.
Solvent model	Computational ChemistrySolvation	A computational representation of a solution environment that incorporates solvent effects on solute structure, energetics, dynamics, and thermodynamics through explicit solvent particles, an implicit continuum, or a hybrid multiscale treatment.
Spectrophotometry	Analytical Measurement	Quantitative measurement of a material's wavelength-dependent transmission, reflection or absorbance by comparing incident and detected electromagnetic intensity.
Spinning drop method	Interfacial Science	An interfacial-tension measurement method that infers very low tension from the equilibrium elongation of a lighter drop in a denser liquid rotating in a horizontal capillary.
Standard enthalpy of reaction	ThermochemistryReaction Energetics	The enthalpy change for a reaction as written when reactants and products occupy their specified standard states at a stated temperature.
Standard state	Physical ChemistryThermodynamic Reference States	A specified thermodynamic reference condition for a substance at a chosen standard pressure and composition convention, used to define activities and tabulate standard-state properties.
Steam reforming	Industrial ChemistryChemical Engineering	Steam reforming or steam methane reforming (SMR) is a method for producing syngas (hydrogen and carbon monoxide) by reaction of hydrocarbons with water.
Stereoisomer	StereochemistryOrganic Chemistry	One of two or more molecular species with the same molecular formula and atom-to-atom connectivity but a different three-dimensional arrangement, classified by whether interconversion requires bond breaking and whether the pair are nonsuperposable mirror images or other diastereomeric forms.
Steric factor	Chemical KineticsCollision Theory	The steric factor, usually denoted ρ, is a quantity used in collision theory.
Sticking Coefficient	Surface ChemistryAdsorption Kinetics	The conditional fraction or probability of incident adsorptive particles that become adsorbed on a specified surface, linking arrival flux to adsorption rate under declared particle, surface, energy, coverage, temperature, and observation-time conditions.
Stoichiometry	Reaction Chemistry	Fix the exact amounts of reactants consumed and products formed from a balanced equation's integer molar ratio and conserved mass, so the reactant shortest in proportion — the limiting reagent — alone caps the theoretical yield.
Structural Formula	Chemical Notation	A chemistry representation that uses governed atom, bond, omission, and optional stereochemical conventions to preserve molecular constitution and selected spatial information that a molecular formula alone does not express.
Structure Field Map	CrystallographyCrystal Chemistry	An empirical materials map that places compositionally comparable crystalline compounds in descriptor coordinates and uses the resulting structure-type fields as an interpretable classification and candidate-structure prior.
Substructure Search	CheminformaticsChemical Structure Retrieval	A chemistry-aware retrieval operation that returns database structures admitting an atom-and-bond embedding of a declared molecular query pattern under explicit matching semantics.
Superhydrophilicity	Surface SciencePhotocatalysis	A surface state in which water spreads almost completely, giving an approximately zero contact angle, often induced on irradiated titanium dioxide and used for antifogging and water-assisted cleaning.
Systematic name	NomenclatureSystematic Identification	A name generated by a codified nomenclature so its components identify one entity and often encode class, structure, composition, rank, or position reproducibly rather than relying on a historical trivial name.
Szyszkowski Equation	Adsorption ThermodynamicsSurface Tension Models	Logarithmic equilibrium relation linking a surface-active solute's concentration to a solution's surface tension relative to a specified clean-interface baseline.
Taft Equation	Physical Organic Chemistry	A physical-organic linear free-energy relationship that separates the effects of aliphatic substituents on reaction rates into polar and steric terms with reaction-series sensitivity coefficients.
Tanabe–Sugano diagram	Coordination Chemistry	A normalized energy-level diagram showing how electronic states of a transition-metal ion vary with ligand-field strength relative to interelectronic repulsion.
Tempering	Heat Treatment of Metals	Reheat a hardened, brittle quenched steel to a sub-critical temperature for a controlled time so carbon diffuses into fine carbides, trading a few hardness points for the toughness the quench alone cannot deliver — a chosen point on the hardness-toughness curve.
Tertiary Carbon	Organic NomenclatureOrganic Chemistry	A carbon atom directly bonded to three other carbon atoms, classified by local carbon–carbon connectivity.
Tetrahedral molecular geometry	Molecular Geometry	A four-coordinate molecular geometry placing substituent directions at the vertices of a tetrahedron around a central atom.
Thermal Desorption Spectroscopy	Surface ScienceAdsorption and Desorption Kinetics	A programmed-temperature surface-analysis method that converts the release of adsorbed species into mass-resolved desorption-rate curves, using peak position, shape, area, and coverage dependence to infer surface populations and desorption kinetics.
Thermodynamic Activity	Chemical ThermodynamicsSolution Thermodynamics	A dimensionless, standard-state-relative expression of a species' chemical potential, defined by a = exp[(mu - mu°)/(RT)] for a specified thermodynamic reference.
Topological insulator growth	Crystal GrowthThin Film Growth	The synthesis of crystalline topological-insulator films or crystals under conditions that control stoichiometry, defects, interfaces, thickness, and van der Waals epitaxy.
Total Analysis System	Analytical ChemistryIntegrated Analytical Systems	An integrated analytical-chemistry device that accepts a sample and automates the linked operations needed to prepare, react, separate, detect, and report its analytes as one end-to-end workflow.
Transferability (chemistry)	Theoretical Chemistry	The modeling assumption that an atom- or functional-group-associated property retains a similar value across related molecular environments.
Transition state	Physical ChemistryReaction Dynamics	The highest-free-energy configuration along a chosen reaction path, defining the dividing surface between reactants and products and controlling reaction-rate theory.
Transition-State Analog	EnzymologyBiochemistry	Transition state analogs (transition state analogues), are chemical compounds with a chemical structure that resembles the transition state of a substrate molecule in an enzyme-catalyzed chemical reaction.
Trigonal bipyramidal molecular geometry	Molecular GeometryVsepr Theory	A five-coordinate molecular geometry with three equatorial ligand positions 120° apart and two axial positions perpendicular to that plane and 180° apart.
Triplet-triplet annihilation	PhotochemistryPhotophysics	Triplet-triplet annihilation (TTA) is an energy transfer mechanism where two molecules in their triplet excited states interact to form a ground state molecule and an excited molecule in its singlet state.
Two-Dimensional Correlation Analysis	Analytical ChemistryChemometricsSpectroscopy	A signal-analysis method that transforms systematic variations measured under an ordered perturbation into synchronous and asynchronous two-dimensional correlation maps, helping resolve overlapping features and infer coordinated or sequential change.
Umpolung	Organic Chemistry	In organic chemistry, umpolung () or polarity inversion is the chemical modification of a functional group with the aim of the reversal of polarity of that group.
Underpotential Deposition	ElectrochemistryElectrodeposition	A metal ion forms a surface-confined adlayer on a different electrode at potentials more positive than bulk deposition of that metal under matched solution conditions.
UNIQUAC	Solution Thermodynamics	A local-composition activity-coefficient model that splits a liquid mixture's excess Gibbs energy into combinatorial size-shape and residual interaction terms.
Universality–diversity paradigm	Biological MaterialsMateriomics	The universality–diversity paradigm (UDP) is the analysis of biological materials based on the universality and diversity of its fundamental structural elements and functional mechanisms.
Valence Bond Theory	Quantum ChemistryChemical Bonding	In chemistry, valence bond (VB) theory is one of the two basic theories, along with molecular orbital (MO) theory, that were developed to use the methods of quantum mechanics to describe chemical bonding.
Van Deemter equation	ChromatographyAnalytical Chemistry	A chromatography rate equation relating plate height to eddy dispersion, longitudinal diffusion, and mass-transfer resistance across mobile-phase velocity.
Vapor Pressure	Chemical Thermodynamics	The pressure of a substance's vapor when that vapor is in thermodynamic equilibrium with a specified condensed phase at a specified temperature.
Variational Transition-State Theory	Chemical KineticsReaction Rate Theory	A chemical rate theory that searches a family of reactant–product dividing surfaces and uses the surface giving the smallest transition-state-theory flux or rate upper bound as the dynamical bottleneck.
Volatile Acid	Contextual Acid Classification	A context-defined class of acids or acid equivalents removable through a vapor or gas pathway, with wine, wastewater, and physiological uses applying different criteria.
Volume concentration	Solution Chemistry	The constituent volume divided by final mixture volume under declared state conditions, reported as a fraction, percentage, or explicit volume-per-volume basis.
Water model	Computational ChemistryMolecular Dynamics	In computational chemistry, a water model is used to simulate and thermodynamically calculate water clusters, liquid water, and aqueous solutions with explicit solvent, often using molecular dynamics or Monte Carlo methods.
Wettability	Chemistry Materials Science	Summarise whether a liquid spreads across or beads off a solid into one measurable scalar — the contact angle set by adhesion versus cohesion — factored into surface chemistry and topography, with two discrete roughness regimes.
Wiener index	Chemical Graph Theory	The sum of shortest-path distances over all unordered vertex pairs of a connected graph.
Wyckoff positions	CrystallographySpace Group Symmetry	The symmetry-equivalence classes of points in a crystallographic space group, classified by conjugate site-symmetry subgroups and tabulated by multiplicity, letter and coordinate constraints.
Zagreb indices	Chemical Graph Theory	Degree-based graph invariants, especially sums of squared vertex degrees or products of endpoint degrees, originally used as molecular topological descriptors.
Zero differential overlap	Computational Quantum Chemistry	A semiempirical quantum-chemistry approximation that neglects selected products of atomic orbitals on different centers, greatly reducing the number of electron-repulsion integrals.
Zeta Potential Titration	Colloid and Interface ScienceAnalytical Chemistry	Controlled addition of acid, base, surfactant, or another reagent to a colloidal dispersion while repeatedly measuring zeta potential to map surface-charge response and locate a zero crossing or operating dose.