Molecular potential energy function and reaction dynamics for LaH2 (C2V, X̃ 2A1)

Abstract

The present work has derived an analytical potential energy function for the ground state (C2V, X̃ 2A1) of LaH2. The electronic state and reasonable dissociation limits are correctly determined based on Atomic and Molecular Reaction Statics (AMRS), and then, using a relativistic compact effective potential (RCEP) for La. The equilibrium geometry, dissociation energy and harmonic frequencies for LaH2 have been calculated by ab initio methods. The results show that R(LaH)=2.1945Å, ∠HLaH=124.4° and De(LaH2)=5.599eV, and ν1, ν2 and ν3 are 1216.521, 1087.417 and 2156.957cm−1, respectively. Molecular reaction dynamics for the collision La(2Dg)+H2(X1Σg+,v=j=0) has been studied based on the analytical potential energy function of LaH2(X̃ 2A1) by using the Monte Carlo quasi-classical trajectory approach. The results for the collision process indicate that the main channel is the exchange reaction La(2Dg)+H2(X1Σg+,v=j=0)→LaH(X1Σ+,v′,j′)+H(2Sg) with the product LaH, and without the formation of the complex compound LaH2. The relationship of the reactive cross-section σr with the relative translational energy Et shows that there is a threshold energy of 40kcal/mol. Because of the tremendous difference in the masses of La and H2, these is a direct collision, and the distributions of the products LaH and H2 are along the direction of forward scattering.