Extension of Gaussian-1 (G1) theory to bromine-containing molecules

Bromine bases suitable for computing G1 energies of bromine-containing molecules have been derived. Our recommended procedure for calculating such energies adopts the G1 steps previously introduced by Pople and co-workers with the following modifications: (i) second-order Mo/ller–Plesset (MP2) geometry optimizations use the polarized, split-valence SV4P basis set for bromine along with 6-31G(d) for first- and second-row atoms; (ii) fourth-order Mo/ller–Plesset (MP4) and QCISD(T) energies are calculated with our new bromine bases along with supplemented 6-311G and McLean–Chandler (MC) 6-311G bases for first- and second-row atoms; and (iii) bromine atomic spin–orbit corrections are explicitly taken into account. G1 energies have been calculated for a selection of simple processes involving bromine-containing molecules. The results obtained are within 0.1 eV of experiment except for the ionization energy of Br2, where the inclusion of molecular spin–orbit corrections is necessary to achieve 0.1 eV accuracy.