Global fit of ab initio potential energy surfaces: II.1. Tetraatomic systems

Global potential energy surfaces (GPES) for general tetraatomic molecular systems which fit ab initio data can be obtained preserving the accuracy of the ab initio points. The global fitting technique is based in a procedure for tetraatomic systems including the functional form previously proposed by the authors. The global fit obtained fulfills the stringent criteria needed for molecular dynamical calculations. The program writes out as output file a Fortran-77 program in a form such that the potential and its derivatives with respect to coordinates can be evaluated readily and accurately at arbitrary geometries.