Quantum chemical study on the structures and isomerization of H_2S_2

MP2 calculations of quantum chemical theory at the 6-311+G(3df,2p)basis set level were used to optimize the reactants,transition states and products with Gaussian program,the corresponding vibrational analysis were calculated at the same level.The transition-state for the unimolecular isomerization was conformed by the intrinsic reaction coordinate(IRC)calculation.Rate constants of the isomerization reaction were evaluated at 300 K by the classical transition state theory.The results demonstrate that the structure of H_2S_2 had two structures:one was linear,the other was branched,the structure of the linear HSSH was stabler;The equilibrium constant was 2.2×10-20 at 300 K.The calculated activation enthalpy for the isomerization process was 195.09 kJ/mol,the reaction rate was pretty slow(only 4.98×10-22 s-1).Thus,the isomerization reaction process was more difficult.