GerritJan Linker

primitives, AO's, LCAO and MO's Starting at the end... MO's are Molecular Orbitals. An MO describes an electron in a molecule. In Hartree Fock calculations the SCFMO's are calculated and their corrsponding orbital energies. LCAO. A MO can be constructed as a Linear Combination of Atomic Orbitals: ψ = ∑_{i}c_{i}Ф_{i} in which ψ is the MO, Ф_{i} is an atomic orbital (AO), the sum is over i atomic orbitals and c_{i} is a coefficient that describes how much AO Ф_{i} contributes to the MO. The coefficients give a sense of what nature a MO has. What AO's contribute predominantly to the MO? AO's. Atomic Orbitals describes electrons in an atom. Atomic orbitals are often named (s, p, d, f, g, h,...). These letters are derived from the characteristics of their spectroscopic lines: sharp, principal, diffuse, and fundamental, ... Atomic orbitals are in their turn built from primitives. We need certain mathematical functions to start build the orbitals with. Different functions are in use, e.g. Slater type functions, Gaussian type functions... Usually a linear combination is made of different primitive functions to make an AO. The coefficients and primitive function used in these combinations are usually fit to give correct atomic properties.
