The Splitting Of Low-lying States For Hydride Molecules (Cations) Of The Ⅱ,Ⅲ Periods Under The Spin-orbit Coupling And The Influence Of An External Field On Small Water Clusters

Using Multi-Configuration Quasi-Degenerate Perturbation Theory(MCQDPT) and Gamess-US, the splitting of low-lying excited states for the hydride molecules (ion molecules) (LiH,BeH,BH,CH,NH,OH,FH,NaH,MgH,AlH,SiH, PH,ClH,SH,LiH⁺,AlH⁺,PH⁺,ClH⁺) of the II,III periods under the spin-orbit coupling(SOC) have been studied in present thesis. And the equilibrium geometric structures and analytical potential functions for the splitting states of these molecules under SOC have been studied; moreover, the spectrum data and coupling value of these splitting have been obtained. It is found that the coupling splitting value increases with the increasing molecular weight. For example, BeH(l3.7863cm¹) and FH⁺(285.1764cm^-1), MgH(28.7746cm^-1) and PH⁺(589.9010cm^-1) in the same period, respectively, and BeH (13.7863cm^-1) and MgH (28.7746cm^-1) in the same group. Based on molecular structures and molecular spectrum and perturbation theory and the spin-orbit coupling theory of the electronic states, for the lighter linear molecules under SOC, the (A,S) coupling scheme is taken, and the specific states of the splitting of the low-lying states are given in our calculation, it is concluded that this coupling scheme is accurate for the lighter molecules.The Murrell-Sorbie potential energy functions for the above diatomic molecules and ions splitting electric states under spin-orbit coupling have been obtained according to the ab initio data through the last-square-fitting. The spectrum data and...