An accurate many-body expansion potential energy surface for AlH2 (22A′) and quantum dynamics in Al(3P) + H2 (v0 = 0–3, j0 = 0, 2, 4, 6) collisions

Abstract

An accurate potential energy surface is constructed for the excited state of AlH₂ by fitting extensive ab initio points calculated at the multi-reference configuration interaction level based on aug-cc-pV(Q+d)Z and aug-cc-pV(5+d)Z basis sets. All the calculated energies are corrected via the many-body expansion method and extrapolated to the complete basis set limit. The various topographic features of the new potential energy surface are investigated to demonstrate the correct behavior of Al(³P) + H₂(X¹Σ_g⁺) and AlH(a³Π) + H(²S) dissociation limits. By employing the time-dependent wave packet approach, the integral scattering cross-sections obtained from the Coriolis coupling calculation and the centrifugal sudden approximation, respectively, are compared in detail and show that the former has a higher effect on the reaction. Moreover, the thermal rate constants for Al(³P) + H₂ (v₀ = 0–3, j₀ = 0, 2, 4, 6) in the temperature range of 0–5000 K are calculated, thereby providing insights into the influence of ro-vibrational quantum numbers on the thermal rate constants.