POTENTIAL-ENERGY SURFACES FOR OSH2

We compute the potential energy surfaces of 12 electronic states of OsH2 (four quintet, four triplet, and four singlet) arising from 5D ground state of the Os atom as well as triplet and singlet excited states using the complete active space multiconfiguration self-consistent field (CAS-MCSCF) followed by multireference configuration interaction (MRCI) and relativistic CI (RCI) calculation which include up to 430,000 configurations. We find that the 5D ground state of Os atom does not insert into H-2 while the excited 3F state of Os does. The B-3(1) ground state of OsH2 (there are two other nearly degenerate states) in the absence of spin-orbit coupling was found to be 22 kcal/mol more stable than Os(5D) + H-2. The spin-orbit mixing of B-3(1), B-3(2), 3A2, and 1A1 states was so strong that it induces significant change in bond angles (up to 10-degrees) for OsH2.