ATOMIC ORBITALS IN MOLECULES

A rigorous definition of atomic orbitals that invokes concepts of the quantum-mechanical theory of atoms in molecules is presented. Being fr ee of any references to nuclei-centered basis functions, this new defi nition is universally applicable to wave functions furnished by all ty pes of electronic structure calculations. The atomic orbitals in molec ules (AOIMs) it produces are continuous and orthonormal. In most cases , linear combinations of only a few such AOIMs accurately represent in dividual molecular orbitals (MOs) and strongly occupied natural orbita ls (NOs). The coefficients of these linear combinations are remarkably insensitive to the quality of basis sets used in the generation of th e MOs and NOs. These properties make the AOIMs particularly suitable f or compact description of bonding in diverse chemical systems. (C) 199 8 American Institute of Physics.