Computational chemistry

Computational chemistry uses mathematical models and computer algorithms to calculate or predict molecular structures, properties, and reactions. Its methods range from quantum-mechanical calculations to simulations based on empirical force fields.

Hartree–Fock method: A quantum-chemical approximation that represents each electron as moving in the average field of all others. It provides a foundational approximation for many electronic-structure calculations.
Schrödinger equation: The equation governing how a quantum system's state changes or is constrained in space. Electronic-structure methods approximate its solutions for atoms and molecules.
Geometry optimization: A numerical procedure for finding molecular coordinates that minimize a calculated energy or another objective function. It predicts stable molecular structures from an initial arrangement of atoms.
Quantum chemistry: The application of quantum mechanics to explain and calculate the properties and behavior of chemical systems. It is the electronic-structure core of computational chemistry, but not its full scope.
Density functional theory: A quantum-mechanical method that calculates electronic properties from the electron density rather than a many-electron wavefunction. It balances useful accuracy and computational cost for many molecular calculations.
Potential energy surface: A function giving a molecular system's potential energy as a function of its nuclear coordinates. Geometry optimization and reaction-path calculations explore this surface.
Reaction mechanism: A sequence of elementary steps describing how reactants become products in a chemical reaction. Calculated pathways and barriers can distinguish competing mechanistic proposals.
Molecular mechanics: A modeling approach that represents atoms and bonds with classical particles and parameterized energy functions. It contrasts with electron-explicit methods in physical detail and computational expense.
Coupled cluster: A family of electronic-structure methods that accounts for electron correlation through an exponential wavefunction ansatz. Its high-accuracy variants serve as benchmarks for smaller chemical systems.
Basis set: A finite collection of mathematical functions used to represent molecular orbitals in electronic-structure calculations. Its size and composition influence both accuracy and computational cost.

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