THEORETICAL-STUDY OF THE RHODIUM DIMER INTERACTION WITH THE HYDROGEN MOLECULE

The C-2 upsilon potential energy surfaces for the end-on and side-on a pproaches of H-2 to the rhodium dimer were studied through self-consis tent-field (SCF) and multiconfigurational SCF calculations, followed b y extensive variational plus second-order multireference Moller-Plesse t Perturbational configuration interaction (CIPSI) calculations. Relat ivistic effective core potentials were used to replace the core electr ons of the rhodium atoms. Together with the Rh-2-H-2 interaction, the spectroscopic constants for the (5) Sigma(g)(+), (1) Sigma(g)(+), 3 Pi (u), and (1) Pi(u) states of Rh-2 are reported. We found that the pote ntial energy curves of the parallel and the perpendicular Rh-2((5) Sig ma(g)) interaction with H-2 show that the rhodium dimer has the abilit y to capture and break the H-2 molecule. The parallel interaction pres ents a soft potential barrier of 7.8 kcal/mol, energy necessary to sur mount before the capture and breaking of the H-H bond. In the perpendi cular interaction, we found that Rh-2 captures and breaks spontaneousl y H-2. The potential energy curve of the parallel Rh-2((1) Sigma(g)) H-2 interaction shows that Rh-2 also captures and breaks spontaneousl y the H-2, with a very deep well of 92.7 kcal/mol, while in the perpen dicular approach, we found that Rh-2 has to surmount again a soft barr ier of 5.2 kcal/mol to capture and break the H-2 molecule. Finally, th e energy curves of the parallel (Rh(2)(1,3)Pi(u)) + H-2 interactions p resent capture and breaking with very small barriers. The perpendicula r interactions capture and scisse the hydrogen molecule spontaneously. (C) 1995 John Wiley & Sons, Inc.