The structures and stability of HAsS2 isomers

The potential energy surface (PES) of HAsS system including nine isomers and ten transition states is investigated at MP2/6-311 + +G(d, p) and QCISD(T)/6-311 + +(3df, 2p) (single-point) levels. On the PES, cis-HSAsS(E1) is found to be thermodynamically and kinctically the most stable isomer followed by trans-HSAsS (E-2) stereo As-S-S three-membered ring HAs (S) S (C-2v, E3), and HAS (S)S(C-s, E4) at 1.46, 60.78, and 93.63 kJ/mol, respectively. Based on the PES. E1, E2, E3 and E4 are kinetically stable isomers, and should be experimentally observable. The products in the first-step reaction of HAS with S-2 can isomerize into isomer E3 that has higher kinetic stability. The direct reaction products of SH with ASS will lead to the formation of isomer E1. The comparison of the calculated results with the PESs of HPO2, HPS2, HNO2, HNS2 and HASO(2) that are analogs of HAsS is investigated.