Accurate potential energy surface of H2S+(X2A″) via extrapolation to the complete basis set limit and its use in dynamics study of S+(D2)+H2(X1Σg+) reaction

Abstract

The single-sheeted potential energy surface (PES) of H2S+(X 2A′′) 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+D2 to S+S4. The many-body expansion formalism is employed to obtain the H2S+(X 2A′′) 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+D2+H2(X1Σg+) → SH+(X 3Σ−)+H(S2) 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.

Accurate Potential Energy Surface for Quartet State HN2 and Interplay of N(4S) + NH(X̃3Σ–) versus H + N2(A3Σu+) Reactions

“…All of these parameters for the NN and NH diatomic potentials have been taken from ref 9. Finally, the exponential decaying portion of the EHF-type energy term assumes the general form 35,36 V R D R a r r ( ) 1 exp( )…”

“…To account for the electronic basis-set incompleteness, we have extrapolated the energies to the complete basis set (CBS) limit using the uniform singlet- and triplet-pair extrapolation (USTE) method, which has been per se or jointly with its generalized version successfully employed in other recent studies of global PESs for a variety of molecular systems. − The extrapolated correlation energy ( E ∞ cor ) is then obtained by fitting to the pair of MRCI+Q/AV T Z and MRCI+Q/AV Q Z calculations for every geometry, thence to the E 3 cor and E 4 cor energies. In the above equation, A 5 (0), c , α, and n are universal parameters, ,− namely, α = −0.375, A 5 (0) = 0.0037685459, c = −1.17847713, and n = 1.25 for the MRCI method.…”

“…All of these parameters for the NN and NH diatomic potentials have been taken from ref . Finally, the exponential decaying portion of the EHF-type energy term assumes the general form , where In eq , r = R – R e is the displacement from the equilibrium diatomic geometry, while D and a i are adjustable parameters to be fitted to the respective MRCI+Q/CBS­( T , Q ) calculations described in Section . Figure a–f shows the final curves, and Table S1 of the Supporting Information (SI) gives the involved numerical data.…”

A global CHIPR potential energy surface of PH2(X2B1) via extrapolation to the complete basis set limit and the dynamics of P(2D) + H2(X1Σ+g) → PH(X3Σ−) + H(2S)

“…The insertion reactions of H 2 with various gaseous atoms or ions have long been a focus of great interest due to their potential applications in interstellar, atmospheric and combustion chemistry. For example, the insertion mechanisms in the CH 2 , 7 NH 2 , 8,9 H 2 O, 10 AlH 2 , 11 and H 2 S + 12 systems had been investigated. The results show that the insertion reaction of a molecular system has a unique characteristic due to the inherent topographical feature of its potential energy surface (PES).…”

Formation of interstellar SH+from vibrationally excited H2: Quantum study of S++ H2⇄ SH++ H reaction and inelastic collision

“…1. In this work the objective is to present a new set of PESs for the quartet and doublet states using a larger electronic basis set than that used by Zanchet et al (2013a) and Song et al (2018).It should be noted that during the preparation of this work, a new PES for the doublet electronic state was also published (Zhang et al 2018) and that QCT calculations were performed for the formation from the excited state of S + ( 2 D). Reactions of H 2 molecules with S + ions in electronic excited states are expected to be negligible inside molecular clouds and only relevant at the PDR/HII interface layers where a small fraction of H 2 might exist.…”