A global potential energy surface for H2S+(X 4A′′) and quasi-classical trajectory study of the S+(4S) + H2(X1Σ+g) reaction

A new global analytical ab initio potential energy surface for the dynamics of the C+(2P) + SH(X2Π) reaction

The global potential energy surface (PES) of HCS⁺(X¹Σ⁺) is constructed using many-body expansion (MBE) methodology. The obtained analytical function is found by fitting the 7907 ab initio energy points computed at the Davidson-corrected multi-reference configuration interaction level with the aug-cc-pV(5+d)Z basis set. The final root mean square error is 0.0419 eV, and the maximum deviation is 0.2039 eV, showing that the analytical formula agrees well with the energy points. The topological features are calculated and discussed based upon the analytical PES of HCS⁺(X¹Σ⁺). The reaction probability, integral cross sections and other details of the C⁺(²P) + SH(X²Π) → H(²S) + CS⁺(X²Σ⁺) reaction are investigated using the quasi-classical trajectory and time-dependent quantum wave packet methods.

A new global potential energy surface of the SH2+(X4A'') system and quantum calculations for the S+ + H2(v = 0-3, j = 0) reaction

A new global potential energy surface (PES) for the ground state of the SH2+(X4A'') system is constructed using a permutation invariant polynomial neural network method. In ab initio calculations, the MRCI-F12 method with the AVTZ basis set is used. Furthermore, the dynamics calculations of the S+ + H2(v = 0-3, j = 0) → SH+ + H reaction are carried out based on the new PES. The reaction probabilities and integral cross sections are compared with available theoretical calculations. Present values are in general good agreement with the previous theoretical studies. However, some discrepancies can still be found due to different PESs used in the calculation. Furthermore, the vibrational energy of the reactant molecule can significantly enhance the reactivity compared to the translational energy. The differential cross sections indicated that the reaction mechanism is changed from the "head-on" rebound mechanism to the tripping mechanism with the increasing number of initial vibrational excitation state.

Accurate potential energy surface of H2S+(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-pVQdZ 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.