The Construction Potential Energy Surface And Dynamics Study Of H+HLi System

The LiH molecules and its radical cations LiH+ have played an important role in the primordial cosmic chemistry, which have received extensive attention on the spectra, polarizability and various electronic states dynamics. A great quantity of studies of the LiH₂ chemical system have been carried out, not only because the LiH molecule and its radical cation LiH+ have taken part in the chemical reaction network in an entirely gaseous phase in the early universe formation, but also the system just has five electrons. It shows many sophisticated features of the complicated chemical species, though the LiH₂ chemical system can be deemed to the next electronically simple neutral triatomic system?after H3? exhibiting bound diatomic asymptotes.After relatively comprehensive literature review, we, knowing that there are controversies on the existence of an earlier barrier, have constructed the H+HLi system full dimensional ground state potential energy surface. The ab initio single point energies are computed using complete active space self-consistent field and multi-reference configuration interaction method with a basis set of cc-p VXZ?X=T, Q, 5? to the complete basis set limit. The many-body expansion procedure is used to describe the analytical potential energy surface function. We try to take more ab initio points?21337? on all triples of the grid defined by 1.0?RLiH/a0?40.0, 0.5? RHH/a0 ? 40.0, 0 ? ?/deg ? 180. The points spread across all reaction channels and concentrated in the area of the entrance channel, export channel and transition state. 21337 ab initio points have been calculated. In order to improve the quality of the fit, ab initio energies below 2.8 eV relative to the energy of the Li-H-H dissociation limit have been chosen to be fitted to analytical forms for the surface which has a rmsd of 0.4991 kcal/mol. When the fixed angle ? is greater than or equal to 60°, the potential energy surface obtained by fitting method is very smooth, and there is no early potential barrier on the H+HLi reaction channel. As the reaction proceeds to release a large amount of energy, late potential barrier is not found in the product channel. We depict the minimum energy paths for the ??Li-H-H? angles fixed at 45°, 90°, 135° and 180°?collinear geometry? for the LiH depletion reaction as function of RLiH-RHH coordinate of the new LiH₂ PES. It is clear that no barrier is noticed in the strong interaction region at the H+HLi channel. Besides, the results of the new fitted PES are closer to the points of ab initio calculations than those of the other two on the H-exchange reaction.Our dynamic results show that H+HLi reaction has no threshold. The integral reaction cross sections decrease with the increase of collision energy and vibrational quantum state. Furthermore, the extent of decrease of cross sections due to the increase of vibrational quantum state gets small with the increase of collision energy. When the collision energy increases 1.0 e V, the change of vibrational quantum state almost has no effect on integral reaction cross sections. In addition, the)?rP ? distributions have the peaks atr? angles near 90° and the peak gets high and narrow with the collision energy increasing. The?(rP ? distributions have the obvious peaks at =90or? and 270°, reflecting the strong polarization of angular momentum for the product. The polarization-dependent differential cross-sections are sensitive to the change of collision energy.