POTENTIAL-ENERGY SURFACES FOR THE INSERTION OF TA AND TA+ INTO H-2

We compute the bending potential energy surfaces of 12 electronic states of TaH2 and TaH2+ using the complete active space multiconfiguration self-consistent field (CAS-MCSCF) followed by multireferences singles + doubles configuration interaction (MRSDCI) calculations. Spin-orbit effects are also included using the relativistic configuration interaction (RCI) approach. We find that the 4F ground state of Ta atom requires a barrier of approximately 24 kcal/mol for insertion into H2 while the 5F ground state of Ta+ does not insert into H-2. The low-spin excited states of Ta and Ta+ are considerably more reactive with H-2. We find three nearly-degenerate bent electronic states of 4B1, 4A2, and 4B2 symmetries as the candidates for the ground state of TaH2. Likewise 3B1 and 3A1 electronic states of TaH2+ are nearly-degenerate candidates for the ground state. The spin-orbit coupling strongly mixes some of these states leading to bond angle changes of up to 10-degrees.