POTENTIAL-ENERGY SURFACES FOR RHH2+

Complete active space multiconfiguration self-consistent-field (CASSCF) calculations followed by multireference singles-plus-doubles configuration interactions (MRSDCI) have been carried out on 12 electronic states of RhH2+. The bending potential energy surfaces of RhH2+ reveal that the a3F ground state of Rh+ forms a complex with H-2 with a geometry of r(e) = 1.737 angstrom, theta-e = 27-degrees, and D(e) = 17.5 kcal/mol relative to Rh+(3F) + H-2. The bending potential energy surface of the 1A1 state of RhH2+ exhibits a double minimum with geometries r(e) = 1.592 angstrom, theta-e = 32-degrees and r(e) = 1.472, angstrom, theta-e = 106.8-degrees at the CASSCF/MRCI level. The acute angle minimum is 0.63 eV more stable than the obtuse angle minimum. The Rh+(a5F) ion needs to surmount a large barrier for insertion into H-2. The adiabatic ionization potential for RhH2 is calculated as 7.4 eV.