Accurate potential energy surface of H 2 S + ( X 2 A ″) via extrapolation to the complete basis set limit and its use in dynamics study of S + ( D 2 ) + H 2 ( X 1 Σ g + ) reaction.

The single-sheeted potential energy surface (PES) of H 2 S + ( X   2 A ' ' ) is developed based on the ab initio energies calculated by the multi-reference configuration interaction method including the Davidson correction. All the ab initio energies are first calculated using aug-cc-pV Q dZ and aug-cc-pV5dZ basis sets, which are then extrapolated to the complete basis set (CBS) limit. A switching function is developed to model the transition of S + D 2 to S + S 4 . The many-body expansion formalism is employed to obtain the H 2 S + ( X   2 A ' ' ) PES by fitting such CBS energies and the root-mean square derivation is 0.0367 eV. The topographical features of the present PES are examined in detail, which are well consistent with previous studies. The quasiclassical trajectory method is subsequently utilized to study the S + D 2 + H 2 ( X 1 Σ g + )   →   S H + ( X   3 Σ - ) + H ( S 2 ) reaction. The capture time, integral cross sections, and rovibrational distributions are calculated. By examining the capture time, it can be concluded that the title reaction is mainly controlled by the indirect mechanism for lower collision energies, while the direct and indirect mechanisms coexist and the latter plays a dominant role for higher collision energies.