Molecular wavefunctions in geminal product approximation

Abstract

A method is presented for the optimization of a molecular wavefunction in the form of an antisymmetrized product of strong-orthogonal geminals. Each geminal function is expressed in a natural orbital expansion, orbitals and expansion coefficients both being fully optimized. An illustrative application is given, confirming the efficiency of the method and the ability of this type of wavefunction to give an accurate description of bond-breaking processes. The connection with valence bond theory is discussed.