Accurate three-dimensional intermolecular potential of the He-MgH complex

An accurate three-dimensional interaction potential energy surface of the He-MgH(2Σ+) van der Waals complex is developed using the partially spin-restricted open-shell single and double excitation coupled cluster method with perturbative triples [RCCSD(T)] level of theory for a large number of geometries. The calculated single point energies at each of five rMgH values are first fitted by an analytic two-dimensional potential model. The five model potentials are then used to construct the three-dimensional potential energy surface by interpolating along (r − re) by a four-order polynomial. Based on the three-dimensional potential energy surface, the vibrational average potential is obtained. Bound state energy levels of He-MgH complex and cross sections for rotational relaxation are calculated within the spin-free approximation.