Accurate electronic structure calculations of a few three-atom systems and low lying states of a diatomic molecule $Pt_2$

Abstract

Closed shell metal cyanides, the Group 1 cyanides and the Group 11 cyanides, were studied with ab initio calculations using recently developed energy consistent pseudopotentials. For each metal cyanide, the most stable conformer was obtained on the potential energy surface and then subjected to the study concerning the relativistic effect. For the Group 1 cyanides, the most stable forms were generally triangular shape. On the other hand, linear cyanide forms were found to be the most stable for the Group 11 cyanides. The fundamental reason for these different results is estimated to be population environment of valence s shell of metal atom. The relativistic effect is larger in the Group 11 cyanides than in the Group 1 cyanides, simultaneously increasing as metal atom becomes heavier. To understand the reaction pathway of the V + NO → VO +N reaction, the potential energy surface was used in obtaining critical points. This reaction was described to energetically favor the pathway going through two triangular conformers. The final product, VO, is obtained entirely as the ground state. The Kramers’ restricted (KR) ab initio calculations were performed for the eight lowest electronic states of $Pt_2$ using the relativistic effective core potential with the spin-orbit operator. We show the importance of the dynamic as well as the nondynamic electron correlation effects to obtain reliable spectroscopic data for this molecule. We have used the multi reference Kramers’ restricted configuration interaction (MR-KRCI) method supplemented with the KR coupled-cluster (CC) method to show this aspect.