Properties of atoms in molecules from valence-electron densities augmented with core-electron contributions

Augmentation of valence-electron densities produced by quantum-chemical calculations involving effective core potentials with transferable, spherically symmetrical core-electron contributions yields accurate approximations to electron densities in molecules. The core-electron contributions, which can be retrieved from Hartree-Fock electronic wavefunctions of isolated atoms, are conveniently represented by sums of s-type Gaussian functions. When used in conjunction with the quantum-mechanical theory of atoms in molecules (AIMs), the augmented valence-electron densities afford atomic charges and multipole moments, together with the valence-electron components of atomic kinetic energies. Test calculations on the TiCl4 molecule demonstrate the excellent performance of the new method.