Coupled quasidiabatic potential energy surfaces for LiFH

High-level ab initio calculations were presented for the coupled quasidiabatic potential energy surfaces for LiFH, using the multireference singles and doubles configuration interaction method. 140 contracted Gaussian functions were present in the basis set, and calculations were performed on a dense grid of ∼3500 nuclear geometries. By fitting physically motivated functional forms to the ab initio data for the two lowest-energy adiabatic states and explicity including long-range interactions, an analytic 2 × 2 quasidiabatic potential energy matrix was obtained.