Ring-polymer molecular dynamical calculations for the F + HCl → HF + Cl reaction on the ground 1²A′ potential energy surface

Abstract

The reaction kinetics of the heavy-light-heavy abstraction reaction F + HCl → HF + Cl on the ground electronic state potential energy surface (PES) is investigated theoretically by a recently developed ring polymer molecular dynamics (RPMD) approach. First, a new PES is developed by the permutation invariant polynomial neural network (PIP-NN) approach based on 30 620 points sampled over a large configuration space from the latest and most accurate Deskevich-Hayes-Takahashi-Skodje-Nesbitt (DHTSN) PES (J. Chem. Phys., 2006, 124, 224303). Excellent fitting performance was achieved with only 521 parameters. The PIP-NN PES is 11 times faster than the DHTSN PES. Besides, the first analytical derivatives with respect to the coordinates of the atoms have been obtained for the PIP-NN PES. The RPMD rate coefficients on the PIP-NN PES are calculated and compared with available theoretical and experimental results. It is found that the experimental rate coefficients are significantly larger than the theoretical results on the DHTSN PES, due to its overestimated reaction barrier. We conclude that a reliable PES for this important heavy-light-heavy reaction is highly desirable.

Revisiting the F + HCl → HF + Cl reaction using a multireference coupled-cluster method

“…The present rate constant practically matches the theoretical results from Sayós et al, 7,8 obtained with a PES whose barrier height was scaled to reproduce the experimental values. This shows, as suggested by some authors, 16,17 that the DHTSN PES has a very large barrier height. The present MRCC PES is the first potential energy surface obtained from first principles that yields for the title reaction a rate constant in close agreement with experiment.…”

“…The dynamics of the chemical reaction F + HCl -HF + Cl has been explored in great detail, [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] but calculations from first principles have not been able to fully reproduce and rationalise the experimental results. 11,[14][15][16][17] This chemical reaction is highly exothermic and proceeds through a small barrier, a transition state with a bent geometry whose ab initio description has been proven to be very challenging. It has multireference character and is affected by two conical intersection seams at collinear geometries.…”

Chemical Reaction Rate Coefficients from Ring Polymer Molecular Dynamics: Theory and Practical Applications

“…4,5 These developments have already benefitted RPMDrate calculations of realistic (non-prototype) reactions. 46,[74][75][76]88 The RPMDrate code was originally developed for the simulation of dynamical processes which can be described by a single PES. 51 There are many chemical events, called non-Born-Oppenheimer reactions or electronically nonadiabatic reactions, which cannot be adequately described within this assumption.…”

Low-Temperature Experimental and Theoretical Rate Constants for the O(1D) + H2 Reaction

“…Consequently, in recent years there has been a significant effort to develop novel theoretical strategies to treat such systems efficiently while simultaneously providing an accurate description of QM effects such as zero-point energy and tunneling. One method, namely ring polymer molecular dynamics (RPMD) rate theory has been demonstrated 41 to provide reliable estimates for insertion type chemical reactions 3,36,[42][43][44][45] as well as for thermally activated chemical reactions [46][47][48][49][50][51][52][53][54][55][56][57][58][59][60][61] and even for reactions with more complex energy profiles. [62][63][64] In particular, RPMD rate constants calculated for a similar chemical reaction between C( 1 D)…”