Molecular potential energy function and reaction dynamics for LaH2 (C-2V, (X)over-tilde (2)A(1))

The present work has derived an analytical potential energy function for th e ground state (C-2V;, (X) over bar (2)A(1)) 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 comp act effective potential (RCEP) for La. The equilibrium geometry, dissociati on energy and harmonic frequencies for LaH2 have been calculated by ab init io methods. The results show that R(LaH) = 2.1945 Angstrom, angle HLaH = 12 4.4 degrees and D-e(LaH2) = 5.599 eV, and nu (1), nu (2) and nu (3) are 121 6.521, 1087.317 and 1156.957 cm(-1), respectively. Molecular reaction dynam ics for the collision La(D-2(g)) + H-2(X(1)Sigma (+)(g), nu = j = 0) has be en studied based on the analytical potential energy function of LaH2((X) ov er bar (2)A(1)) by using the Monte Carlo quasi-classical trajectory approac h. The results fur the collision process indicate that the main channel is the exchange reaction La(D-2(g)) + H-2(X(1)Sigma (+)(g), nu = j = 0) --> La H(X(1)Sigma+, nu',j') + H(S-2(g)) with the product LaH, and without the for mation of the complex compound LaH2. The relationship of the reactive cross -section sigma (r), with the relative translational energy E-tau, shows tha t there is a threshold energy of 40 kcal/mol. Because of the tremendous dif ference in the masses of La and ill, these is a direct collision, and the d istributions of the products LaH and H-2 are along the direction of forward scattering. (C) 2000 Elsevier Science B.V. All rights reserved.