The potential energy surfaces of ground state of He—HBr complex have been calculated at several levels of theory, including the single and double excitation coupled-cluster method with noniterative perturbation treatment of triple excitation CCSD(T). Calculations have been performed using the augmented correlation-consistent polarized quadruple zeta basis set (aug-cc-pVQZ). Using the complete basis set (CBS), the global minimum with a well depth of approximately 28.792 cm~ (-1) has been found for the linear He—H—Br geometry (θ = 0.0°) with the distance R between the He atom and the center of mass of the HBr molecule equal to 0.407 nm. In addition to the global minimum, there is a second minimum at R = 0.343 nm and θ = 180°(a well depth of 35. 707 cm~(-1)). Finally the effects of the basis sets and theoretical methods on the intermolecular potential are discussed and a simple analytic form employing 17 adjustable parameters for fitting to the calculated PES is given.

Key words: AB INITIO CALCULATION, He, Ne, HBr, HF, HCl