d-Orbital sizes in the snpmd, sn–1pmd2, and snpm–1d2 configurations of some second-row elements

Abstract

Wavefunctions and HF energies for configurations of Al, Si, P, S, and Cl with single and double promotions to d levels are reported. Fully SCF numerical methods are employed for their evaluation, and comparisons are made among d-orbital 〈r〉 values along the series of elements. Single and double excitation processes lead to remarkably different values for the outer d orbitals, and their contributions to ‘reactive’ state configurations are discussed within the framework of the Van Vleck vector model for valence states. Promotion energies and r_m values for 3d electrons are also reported. Mean radii contractions after double excitation (affecting overlap integrals among bonding orbitals) are shown to depend clearly upon the atomic number Z, e.g., r_m^3d values go from 1·94 in P to 1·80 in S and 1·44 Å in Cl.