A Full-Dimensional Global Potential Energy Surface of H₃O⁺(ã³A) for the OH⁺(X̃³Σ^–) + H₂(X̃¹Σ_g⁺) → H(²S) + H₂O⁺(X̃²B₁) Reaction

Abstract

An accurate full-dimensional global potential energy surface (PES) is developed for the title reaction. The PES was based on ∼30,000 points at the Davidson corrected multireference configuration interaction level with the aug-cc-pVQZ basis set (MRCI+Q/AVQZ). The ab initio points were fitted using the permutation invariant polynomial-neural network (PIP-NN) method with a root-mean-square error of about 3.0 meV or 24 cm(-1). The kinetics of the OH(+) + H2 and OH(+) + D2 reactions were investigated on the PIP-NN PES using a quasi-classical trajectory method and the calculated thermal rate coefficients are in good agreement with the available experimental data. Furthermore, it is predicted based on the PES using the Sudden Vector Projection model that the rotational excitation of OH(+) enhances the reaction at low collision energies.

Low temperature rates for key steps of interstellar gas-phase water formation

“…Careful comparison between the RPMD approximation and exact quantum dynamical theory has been carried out recently for many prototypical reactions ( 35 ), including several barrierless complex-forming reactions similar to reactions (1) to (3), and the agreement has been very encouraging. Here, we focus on reactions (1) and (2), using recently developed full-dimensional potential energy surfaces based on fitting a large number of high-level ab initio data and augmented with analytical long-range interaction terms ( 26 , 36 ). Note that we did not distinguish the ortho- and para-H 2 in our calculations, and we assumed the H 2 rotational distribution to be Boltzmann.…”

“…The uncertainties for the present RPMD calculations represent the convergence limit within two SDs. Also shown are previous room temperature measurements; for clarity, they are shifted in steps of 10 K. Theoretical calculations (RPMD and QCT) were performed using potential energy surfaces (PESs) from ( 26 , 36 ). References for previous room temperature data are as follows: Shul et al .…”

“…The key features of RPMD that lead to this success are (i) exact classical high-temperature limit, (ii) independence of the choice of transition state dividing surface, and (iii) connection to various transition state theories in the short-time limit ( 35 ). Here, we used the PESs for the title reactions (1) and (2) from ( 26 , 36 ). …”

Reactive atomistic simulations of Diels-Alder reactions: The importance of molecular rotations

“…The present work suggests that rotations can play an important role for reactions involving large excess of translational energy and the implications for reaction dynamics involving polyatomic molecules are exciting. [55][56][57][58][59] As a next step, we intend to perform reactive molecular dynamics simulations for the cationic reaction between DBB and MA that is expected to be faster and in which concerted and stepwise mechanisms are anticipated to coexist. 23 To the best of our knowledge, no simulation study had been performed in Diels-Alder reactions starting from the beginning of the reaction without steered dynamics.…”

REACTION STUDIES OF NEUTRAL ATOMIC C WITH ${{\rm{H}}}_{3}^{+}$ USING A MERGED-BEAMS APPARATUS

“…Talbi et al (1991) and Bettens & Collins (1998, 2001 carried out their calculations at 10 K. In their work, they treat the reaction adiabiatically and ignore surface crossing and intersystem transitions. This approach is still standard for theoretical rate coefficients (Klippenstein et al 2010;Li & Guo 2014). Additionally, Talbi et al (1991) and Bettens & Collins (1998, 2001 extrapolated to temperatures up to 300 K by multiplicatively scaling their results to account for the temperature dependence of fractional populations of the attractive surfaces involved in the reaction.…”