First principles study of cobalt hydride, CoH, and its ions CoH+ and CoH−

Abstract

The electronic structure of the diatomic species CoH, CoH(+), and CoH(-) have been studied mainly by multireference configuration interaction (MRCI) methods and basis sets of quintuple quality. The restricted coupled-cluster with iterative singles + doubles + quasi-perturbative connected triples, RCCSD(T), approach was also employed, limited however to the ground states only. At the MRCI level we have constructed 27 (CoH), 24 (CoH(+)), and 12 (CoH(-)) potential energy curves correlating adiabatically to six, seven, and two energy channels, respectively. For the ground states scalar relativistic and core-subvalence effects have been taken into account. We report energetics, spectroscopic parameters, dipole moments, excitation energies, and spin-orbit coupling constants. Our CoH calculated results are in accord with experiment, but there is an interesting discrepancy between theory and experiment concerning the dipole moment, the former being significantly larger than the latter. Experimental results on CoH(+) and CoH(-) are scarce. The ground state of CoH, CoH(+), and CoH(-) are definitely of (3)Φ, (4)Φ, and (4)Φ symmetries with calculated (experimental) dissociation energies D(0)(0) = 46.4 ± 0.5(45.0 ± 1.2), 49.6(47 ± 2), and 45.6(43.1 ± 1.2) kcal/mol, respectively. In all 24 calculated CoH states, a Co-to-H charge transfer of 0.2-0.3 e(-) is recorded; in CoH(-), however, the negative charge resides almost exclusively on the Co atom.