Stereodynamics of the reaction H+LiH (v=0,j=0)→H2+Li and its isotopic variants

Influence of rovibrational excitation on the non-diabatic state-to-state dynamics for the Li(2p) + H2 → LiH + H reaction

The non-adiabatic state-to-state dynamics of the Li(2p) + H2 → LiH + H reaction has been studied using the time-dependent wave packet method, based on a set of diabatic potential energy surfaces recently developed by our group. Integral cross sections (ICSs) can be increase more than an order of magnitude by the vibrational excitation of H2, whereas the ICSs are barely affected by the rotational excitation of H2. Moreover, ICSs of the title reaction with vibrationally excited H2 decrease rapidly with increasing collision energy, which is a typical feature of non-threshold reaction. This phenomenon implies that the title reaction can transformed from an endothermic to an exothermic reaction by vibrational excitation of H2. With the increase of the collision energy, the sideways and backward scattered tendencies of LiH for the Li(2p) + H2(v = 0, j = 0, 1) → LiH + H reactions are enhanced slightly, while the backward scattering tendency of LiH for the Li(2p) + H2(v = 1, j = 0) → LiH + H reaction becomes remarkably weakened. For the reaction with vibrationally excited H2 molecule, both direct and indirect reaction mechanism exist simultaneously.

A new potential energy surface for the ground state of the LiH2+system and dynamic studies on LiH+(X2Σ+) + H(2S) → Li+(1S) + H2(X1Σ+g)

An accurate potential energy surface for the ground state of the LiH₂⁺system is constructed with the neural network method.

Global diabatic potential energy surfaces and quantum dynamical studies for the Li(2p) + H2(X(1)Σ(+)g) → LiH(X(1)Σ(+)) + H reaction

The global diabatic potential energy surfaces which are correlated with the ground state 1A' and the excited state 2A' of the Li(2p) + H2 reaction are presented in this study. The multi-reference configuration interaction method and large basis sets (aug-cc-pVQZ for H atom and cc-pwCVQZ for Li atom) were employed in the ab initio single-point energy calculations. The diabatic potential energies were generated by the diabatization scheme based on transition dipole moment operators. The neural network method was utilized to fit the matrix elements of the diabatic energy surfaces, and the root mean square errors were extremely small (3.69 meV for , 5.34 meV for and 5.06 meV for ). The topographical features of the diabatic potential energy surfaces were characterized and the surfaces were found to be sufficiently smooth for the dynamical calculation. The crossing seam of the conical intersections between the and surfaces were pinpointed. Based on this new analytical diabatic potential energy surfaces, time-dependent wave packet calculation were conducted to investigate the mechanism of the title reaction. At low collision energies, the product LiH molecule tends to forward scattering, while at high collision energies, the forward and backward scatterings exist simultaneously.

Collision time of a triatomic chemical reaction A + BC

The collision time is an important quantity of an elementary chemical reaction and describes the speed of the collision process in a collision reaction. In this study, we present a generalized method to calculate the collision time of a triatomic reaction in which the collision time is defined by the sum of the incoming time, the intermediate complex time, and the outgoing time. Two variables including the total distance Rtotal and Ravg, the average value of Rtotal over time, are used to compute the three components of the collision time. We compute three triatomic reactions including Ca + HCl → CaCl + H, O + HCl → OH + Cl/OCl + H, and O + HF → OH + F at different collision energies and initial diatomic vibrational levels using the quasi-classical trajectory method to confirm that the method could be reliable and reasonable. The time evolutions of Rtotal could efficiently classify the direct and indirect reactive mechanisms and reveal a distinct discrepancy of the two mechanisms. As the collision energy and initial diatomic vibrational level increase, the percentage of direct reaction trajectories increases. At the same time, the average and maximal values of collision time decrease. Comparing the maximal collision time and the reactive probability distributions of the products, it could be found that most reactive trajectories’ collision time is less than 2 ps. Moreover, the present calculations indicate that the method could be applicable to estimate the lifetime of the intermediate complex for the reaction systems with deep potential wells and the collision time of the reactions with a direct abstraction mechanism.