A DFT and ab initio direct dynamics study on the hydrogen abstract reaction of H3BNH3 → H2+H2BNH2

A direct A initio dynamics study is presented on the hydrogen abstraction reaction of H3BNH3 --> H-2 + H2BNH(2). The geometries of all the stationary points are optimized at the B3LYP and MP2 levels of theory with a series of basis sets up to aug-cc-pVTZ. The energies are refined using the G3, G3MP2, G3MP2B3, CBS-Q CBS-Q//B3, and a combined high-level (HL) method based on the geometries optimized using the B3LYP/aug-cc-pVTZ level of theory. The rate constants are evaluated using the conventional transition-state theory and canonical variational transition-state theory (CVT). The fitted Arrhenius expression calculated from the CVT/SCT method is k(T) 6.86 x 10(6) x T-1.69 x e((-1.37x104/T)) s(-1). The estimated apparent activation energy is in accordance with experimental results. (C) 2005 Elsevier B.V. All rights reserved.