Characterization of the X~2A_1,A~2B_1,and X~2 PI electronic states of the Ga_2H molecule and the X~2A' and A~2A' isomerization transition states connecting the three minima

摘要

A wide range of highly correlated ab initio methods has been used to predict the geometrical parameters of the linear (X~2PI) and H-bridged (X~2A_1 and A~2B_1,) Ga_2H isomers and two isomerization transition states (X~2A' and A~2A") connecting the three minima.Dipole moments and vibrational frequencies are also obtained.The global minimum X~2A_1,ground state of the H-bridged GaHGa isomer is predicted to lie only 1.6 [1.9 with the zero-point vibrational energy (ZPVE) corrections] kcal mol~(-1) below the A~2B_1 state.The X~2A_1 state lies 5.4 kcal mol~(-1) below the X~2PI ground state of the linear GaGaH isomer at the coupled-cluster with single,double,and perturbative triple excitations [CCSD(T)] level of theory with the augmented correlation-consistent polarized valence quadruple-zeta (aug-cc-pVQZ) basis set.The full triples coupled-cluster method is found to alter these CCSD(T) predictions by as much as 0.3 kcal mol~(-1).The forward isomerization barriers from the linear ground state to the X~2A' and A~2A" transition states are determined to be 3.3 and 5.3 kcal mol~(-1),respectively.The reverse isomerization barrier between the X~2A_1 GaHGa structure and the X~2PI GaGaH structure is predicted to be 8.6 (8.2 with the ZPVE corrections) kcal mol~(-1) at the aug-cc-pVQZ CCSD(T) level of theory.