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)

Abstract

A global potential energy surface (PES) for the electronic ground state of PH₂(X²B₁) is reported based on accurate ab initio energy points and analytically modeled using the combined-hyperbolic-inverse-power-representation (CHIPR) method. A total of 12 339 ab initio energy points are calculated by the multireference configuration interaction method with the Davidson correction and extrapolated to the complete basis set limit using the aug-cc-pV(T + d)Z and aug-cc-pV(Q + d)Z basis sets. A switching function is constructed to model the transition between P(²D) and P(⁴S) to ensure the reliable behaviors at dissociation limits. The ab initio potential energy curves of H₂(X¹Σ⁺_g) and PH(X³Σ⁻) are refined by a multi-attribute fitting to previous experimental spectroscopic constants. The analytical CHIPR PES reproduces well with the ab initio energy points with a root mean square deviation of 41.7 cm⁻¹. The topographical features of the CHIPR PES are examined and discussed in detail, and they agree well with those of the previous work. The quasi-classical trajectory method is utilized to calculate the integral cross sections and thermal rate constants for the insertion reaction of P(²D) + H₂(X¹Σ⁺_g) → PH(X³Σ⁻) + H(²S). The results show a typical characteristic of the endothermic reaction with a barrier and this PES can be a reliable component for constructing the PESs of PH₃ or other larger molecular systems containing PH₂.