Molecular orbital theory overlap matrix

Mulliken population analysis is in the general spirit of the scheme used in the simple Hiickel method, but allows for several basis functions on an atom and does not require the overlap matrix to be a unit matrix. In ab initio theory each molecular orbital has a wavefunction ijj (Section 5.2.3.6.1) ... 

HF theory is one of the most important methods in quantum chemistry. Used by itself, it produces good qualitative descriptions of molecular systems. Additionally, many quantitative descriptions of molecules build upon the HF result, first requiring a solution of the HF equations. The basic problem in HF theory is to solve the Roothaan equations, which can be written as the matrix eigenvalue problem, FC = SCe, where F is the Fock matrix and S is the overlap matrix. We solve for C, the orbital coefficients, and the eigenvalues, e. For closed-shell molecules, the electron density of the system, D, is related to C by... 

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