Global diabatic potential energy surfaces for the BeH 2 + system and dynamics studies on the Be + ( 2 P) + H 2 (X 1 Σ g + ) → BeH + (X 1 Σ + ) + H( 2 S) reaction.

The Be + ( 2 P) + H 2 (X 1 Σ g + ) → BeH + (X 1 Σ + ) + H( 2 S) reaction has great significance for studying diabatic processes and ultracold chemistry. The first global diabatic potential energy surfaces (PESs) which are correlated with the lowest two adiabatic states 1 2 A' and 2 2 A' of the BeH 2 + system are constructed by using the neural network method. Ab initio energy points are calculated using the multi-reference configuration interaction method with the Davidson correction and AVQZ basis set. The diabatic energies are obtained from the transformation of ab initio data based on the dipole moment operators. The topographical characteristics of the diabatic PESs are described in detail, and the positions of crossing between the V d 11 and V d 22 are pinpointed. On new diabatic PESs, the time-dependent quantum wave packet method is carried out to study the mechanism of the title reaction. The results of dynamics calculations indicate the reaction has no threshold and the product BeH + is excited to high vibrational states easily. In addition, the product BeH + tends to backward scattering at most collision energies.