| Abstract
| - The three lowest diabatic potential energy surfaces for the Br(2P) + H2 van der Waals complex are derivedfrom accurate ab initio calculations of the T-shaped (C2v) and collinear geometries (C∞v), at the coupledcluster with single, double, and noniterative triple excitations (CCSD(T)) level of theory with a large basisset. For the intermediate geometries, the angular dependence is modeled by a simple Legendre-polynomialinterpolation. The nonadiabatic coupling (off-diagonal derivative) matrix element and the fourth, off-diagonal,diabatic surface are determined by separate complete active space self-consisted field (CASSCF) calculationswith a medium-sized basis set. Three adiabatic potential energy surfaces (PESs) are also obtained, bydiagonalizing the total Hamiltonian in the diabatic basis. Both the nonrelativistic and relativistic (includingspin−orbit coupling) PESs are evaluated. The dependence of the PESs on the H2 stretching coordinate is alsoincorporated and analyzed.
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