Extension of Gaussian-2 theory to molecules containing third-row atoms Ga–Kr

TLDR

Basis sets compatible with G2 for first‑ and second‑row atoms have been derived, and spin–orbit corrections for spatially degenerate states are explicitly incorporated into the G2 energies. The extended G2 theory yields an average absolute deviation of 1.37 kcal/mol for 40 test reactions, a substantial improvement over the 2.36 kcal/mol error without spin–orbit effects, highlighting the necessity of including spin–orbit corrections for third‑row molecules.

Abstract

Gaussian-2 (G2) theory has been extended to molecules containing the third-row nontransition elements Ga–Kr. Basis sets compatible with those used in G2 theory for molecules containing first- and second-row atoms have been derived. Spin–orbit corrections for atoms and molecules having spatially degenerate states (2P, 3P for atoms and 2Π for molecules in this work) are included explicitly in the G2 energies. The average absolute deviation from experiment for 40 test reactions is 1.37 kcal/mol. In contrast to the situation for first- and second-row molecules, inclusion of spin–orbit effects is very important in attaining accurate energies for molecules containing third-row atoms. Without spin–orbit effects, the average absolute deviation is 2.36 kcal/mol.