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

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.