Accurate double many‐body expansion potential energy surface by extrapolation to the complete basis set limit and dynamics calculations for ground state of NH₂

Abstract

An accurate single-sheeted double many-body expansion potential energy surface is reported for the title system. A switching function formalism has been used to warrant the correct behavior at the H2(X1Σg+)+N(2D) and NH (X3Σ-)+H(2S) dissociation channels involving nitrogen in the ground N(4S) and first excited N(2D) states. The topographical features of the novel global potential energy surface are examined in detail, and found to be in good agreement with those calculated directly from the raw ab initio energies, as well as previous calculations available in the literature. The novel surface can be using to treat well the Renner-Teller degeneracy of the 12A″ and 12A' states of NH 2. Such a work can both be recommended for dynamics studies of the N(2D)+H2 reaction and as building blocks for constructing the double many-body expansion potential energy surface of larger nitrogen/hydrogen-containing systems. In turn, a test theoretical study of the reaction N(2D)+H2(X1Σg+)(ν=0,j=0)→NH (X3Σ-)+H(2S) has been carried out with the method of quantum wave packet on the new potential energy surface. Reaction probabilities, integral cross sections, and differential cross sections have been calculated. Threshold exists because of the energy barrier (68.5 meV) along the minimum energy path. On the curve of reaction probability for total angular momentum J = 0, there are two sharp peaks just above threshold. The value of integral cross section increases quickly from zero to maximum with the increase of collision energy, and then stays stable with small oscillations. The differential cross section result shows that the reaction is a typical forward and backward scatter in agreement with experimental measurement result.

A new potential energy surface for the ground electronic state of the LiH2 system, and dynamics studies on the H(2S) + LiH(X1Σ+) → Li(2S) + H2(X1Σg+) reaction

“…Due to the difference, the physical pictures obtained from the two PESs were obviously different especially at low collision energy [29]. Up to now, many fitting methods have been developed, and the most common one is many-body expansion which is used widely to construct PESs [30][31][32]. In this work, we report an accurate global PES for the lowest doublet state of LiH2 ( 2 A′) system.…”

Globally accurate potential energy surface for the ground-state HCS(X2A′) and its use in reaction dynamics

“…Other theoretical2223242526272829303132 and experimental33 values are also gathered in this table for comparison. It can be found that the present values are in good agreement with results from other literatures.…”

“…Both aug-cc-pV Q Z (AV Q Z) and aug-cc-PV5Z (AV5Z) atomic basis sets have been employed. In order to improve the accuracy of PES, such obtained ab initio energies are then extrapolated to the complete basis-set (CBS) limit222324252627. Based on the adiabatic PES, the reaction dynamics of C + SH reaction were investigated using the quasi-classical trajectory (QCT) method.…”

Accurate equilibrium inversion barrier of ammonia by extrapolation to the one-electron basis set limit

“…Built in a systematic manner, which is intended to relate the correlation energy to the cardinal number X, Dunning's correlation consistent basis sets [28] allow the raw energies to be extrapolated to the one-electron CBS limit. [29][30][31] To perform the extrapolation, by carrying out calculations for several values of X, one may then exploit the X dependence of the calculated energy E X to obtain its value E ∞ in the CBS limit.…”