Ab initio study of the CuPt 3 cluster with H 2 interaction

The CuPt 3 cluster with H 2 interaction was studied by means of Hartree–Fock self‐consistent field (HF‐SCF) and multiconfigurational SCF plus variational and multireference second‐order Möller–Plesset perturbational configuration interaction (CIPSI) calculations, using relativistic core potentials. The CuPt 3 ‐H 2 interaction was carried out in C s symmetry for both: the H 2 in the C s reflecting plane and bisected by the C s reflecting plane. The valence electronic configuration and energy separation of the three low‐lying states of CuPt 3 tetrahedral pyramid cluster was determined: 2 A″, 2 A′, and 4 A′ electronic states. We found that the ( 2 A″) ground state captures and dissociates H 2 without energy barriers only by a Pt vertex of the CuPt 3 cluster. Also, the CuPt 3 cluster, in its ( 2 A′) first excited state, by the Cu or Pt center can capture and dissociate the H 2 molecule. Meanwhile, the same state for the CuPt 2 and Pt 3 face can capture and break H 2 . We have found that CuPt 3 cluster in its ( 4 A′) second excited state spontaneously activates and breaks the hydrogen molecule, with some exception, when H 2 is approaching to a copper vertex. In this work we found that the CuPt 3 ‐H 2 and Pt 4 ‐H 2 interactions show similar capture and activation of H 2 behaviors such as depth of wells, barriers, adsorption distances, and HH bond relaxation. Even in the case of a single Pt atom substitution by a Cu in a Pt 4 cluster, there is no loss of the H 2 activity compared with pure metal cluster. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002