ABINITIO SCF AND MOLLER-PLESSET STUDIES ON HEXACHLORIDES OF SELENIUM AND TELLURIUM AND THEIR DIANIONS

SCF and Moller-Plesset calculations were done for four chalcogen hexahalide systems (SeCl6, SeCl62-, TeCl6, and TeCl62-) to study their geometric structures and relative stabilities in their ground electronic states. Flexible all-electron and valence-electron polarized basis sets were used. For some of the basis sets used, the stationary points located on the SCF potential energy surface of the ions in O(h) symmetry were found to possess negative eigenvalues of the Hessian matrix; the structural parameters of the corresponding stationary points in C3v symmetry were determined. At the MP2 level. all ions were found to restore the octahedral symmetry.