The Potential Energy Profile of the HBr⁺ + HCl Bimolecular Collision

Abstract

Recently, the HBr + + HCl bimolecular reaction has been exploited by guided ion beam studies to probe the effect of rotational excitations and collision energies on the dynamics of the ion−molecule reactions. The current manuscript employs high-level ab initio calculations and reports the potential energy of pathways leading to various products, including HBr + HCl + , H 2 Cl + + Br, H 2 Br + + Cl, and H 2 + BrCl + . The study shows that the intermediates involved in this reaction are connected by lowlying transition states, thus frequent isomerizations and diverse products are expected. Further, this manuscript screens the performance of 192 different combinations of computationally efficient methods and basis sets in order to identify the optimal quantum chemical method for further dynamics simulations.

The potential energy profile of the decomposition of 1,1-diamino-2,2-dinitroethylene (FOX-7) in the gas phase

“…The system is allowed to relax following the energy gradient. 40,41 The dissociation of a target intermediate to separated molecules will be considered barrierless if both the distance and the potential energy of the system monotonically decrease until the system configuration relaxes to the target intermediate. Natural bond orbital (NBO) analysis [42][43][44] is carried out by the Mayer bond order extension 45 compiled in Multiwfn (Version 3.8) 46 to analyze the bond order and the bond strength.…”

Ion–molecule reactions in the HBr+ + HCl (DCl) system: a combined experimental and theoretical study

“…In these reactive trajectories, HBr + and HCl preferentially orient themselves to form i3 in ref. 46, which can then form the PT product, as illustrated in the bottom panel of Fig. 7.…”

“…An overview on capture theory models has been reported recently. 45 Ab initio molecular dynamics simulations An accurate potential energy profile of the HBr + + HCl reaction has been previously characterized at the CCSD(T)/cc-pVDZ// CCSD(T)/CBS level by Fujioka et al 46 In the current work, this reaction is studied using the AIMD simulation, in which the system is propagated iteratively based on the force computed on the fly using quantum chemistry methods. After comparing various combinations of the DFT/MP2 and basis sets, frozencores (FC)mp2 47 /aug-pc-1 48 and FCmp2/def2-SVP 49 were reported to be the optimal methods for the AIMD.…”

“…See the ESI † for more details). With a similar level of excess energy, the cross section of PT of the HCl + + HCl collision (85.1 Å 2 ) 46 is overall larger than that of the HBr + + HCl reaction, which could be related to the energy difference in the exit channel: 0.55 eV for HCl + + HCl vs. 0.67 eV for HBr + + HCl. The impact of reaction energetics is demonstrated in the CT reaction in these two cases -the CT reaction of HCl + + HCl is isothermal and its cross section is non-negligible: 3.1 AE 0.8 (0.2 eV), 5.4 AE 1.1 (0.5 eV), and 3.7 AE 0.9 Å 2 (1.0 eV), which are 3.6%, 11.7%, and 14.2% of the cross section of the PT reaction under same conditions.…”

Directed gas phase preparation of ethynylallene (H2CCCHCCH; X1A′) via the crossed molecular beam reaction of the methylidyne radical (CH; X2Π) with vinylacetylene (H2CCHCCH; X1A′)

“…In this study, further comparison was made with different basis sets before the most accurate, aug-pc-1, 78 was chosen with respect to the benchmark potential energy surface. The minimal root mean square displacement (RMSD) between the benchmark and candidate combination's energies 79 is used to measure the accuracy of the method while the average time per energy gradient calculation ( t ) is used to measure the efficiency. In general, AIMD seeks to employ the most accurate methods while being affordable, and as a result, B3LYP/aug-pc-1 was selected.…”