Four-body singlet potential-energy surface for reactions of calcium monofluoride

A full six-dimensional Born-Oppenheimer singlet potential-energy surface is constructed for the reaction CaF  +  CaF  → CaF 2   +  Ca using a multireference configuration-interaction electronic structure calculation. The ab initio data thus calculated are interpolated by Gaussian process regression. The four-body potential-energy surface features one  D 2 h  global minimum and one  C s  local minimum, connected by a barrierless transition state that lends insight to the reaction mechanism.