Coupled cluster calculations using relativistic effective core potentials and ab initio calculations of $M^*$ + $H_2$ → MH + H reactions and silatranes

Abstract

We have implemented two-component Kramers`` restricted coupled-cluster single and doubles with triples perturbatively(KRCCSD(T)) using relativistic effective core potential(REP) with one-electron spin-orbit operator. Basis sets of the pVTZ quality are genergated for the REP for several atoms. Using these basis sets we calculated molecular properties by the KRCCSD methods. The results are in good agreement with those of all-electron Dirac-Coulomb calculations. The spin-orbit effects on the transition state are investigated for the X + HX → XH + X reactions(where X=Cl, Br, I). Potential energy sufraces for the $M^*$ + $H_2$ → MH + H reactions(where M=Li, Na, K) are generated using extensive configuration methods. From the generated potential energy surfaces we have shown the nature of the reaction. The charge of alkali atoms partially moved to the hydrogen molecules but the harpooning model cannot be applied to these reactions. We optimized the 1-fluorosilatrane and silatrane cation at HF, MP2, and various hybrid DFT level using several basis sets. The N → Si bond distance of 1-fluorosilatrane agrees with the gas phase experimental value when the Perdew-Wang correlation functional is used in the hybrid DFT calculations. In the MP2 calculation the bond distance is shorter than that of hybrid DFT calculations. By NBO analysis we analyze the character of N → Si bond. The d character of Si atom joins in the bonding as much as the p character of Si atom at the MP2 calculations. In the hybrid DFTcalculations the N atom doesn``t give the lone pair to Si atom when we analyze the bonding character using the NBO method. In the analysis based on the quantum chemistry for many molecules and reactions we can show the good results by generating of basis sets and implementing the methods including the spin-orbit effects. We can explain and expect the results of the experiments on the basis of theoretical methods.