Potential energy surfaces for insertion of nickel ion(1+), palladium ion(1+), and platinum ion(1+) into hydrogen

Abstract

Potential energy surfaces of eight electronic states of NiH{sub 2}{sup +}, four quartet electronic states of PdH{sub 2}{sup +}, and eight electronic states of PtH{sub 2}{sup +} are computed. Complete active space self-consistent-field (CASSCF) calculations followed by multireference configuration interaction (MRCI) calculations are carried out. Spin-orbit effects are considered with the relativistic configuration interaction (RCI) method. The ground states of NiH{sub 2}{sup +} and PtH{sub 2}{sup +} are both the {sup 2}A{sub 1} bent electronic states, although in contrast with NiH{sub 2}{sup +}, PtH{sub 2}{sup +} forms a relatively large-angle minimum in the absence of spin-orbit coupling. The Ni{sup +}(a{sup 2}D) and Pt{sup +} ({sup 2}D) states insert spontaneously into H{sub 2} to form the NiH{sub 2}{sup +} and PtH{sub 2}{sup +} molecular ions along the {sup 2}A{sub 1} potential energy surfaces, yielding the bent ground states which are 22 and 28 kcal/mol more stable than Ni{sup +}({sup 2}D) + H{sub 2} and Pt{sup +}({sup 2}D) + H{sub 2} in the absence of spin-orbit coupling, respectively. The spin-orbit coupling mixes the {sup 2}A{sub 1} and {sup 2}A{sub 2} states of PtH{sub 2}{sup +} substantially, thereby stabilizing the small-angle minimum compared to the large-angle minimum. This leads to a different groundmore » state with a different geometry when spin-orbit coupling is included for PtH{sub 2}{sup +}. Mulliken populations of Ni{sup +} and Pt{sup +} in the ground states of NiH{sub 2}{sup +} and PtH{sub 2}{sup +} are Ni{sup +}(rs{sup 0.31}4p{sup 0.12}3d{sup 8.77}) and Pt{sup +}(6s{sup 0.80}6p{sup 0.07}5d{sup 8.34}), respectively, which suggest that the 6s participation is enhanced for Pt{sup +} due to the relativistic effects. 26 refs., 3 figs., 10 tabs.« less