Calculation of Rydberg potential energy curve from Murrell–Sorbie parameters

Abstract

Potential functions that that possess larger number of parameters generally provide better descriptions of interatomic energy owing to the greater flexibility in curve fitting. However, most molecular mechanics and computational solid state softwares adopt simple potential functions in order to reduce the computation time. This paper discusses three methods for converting the extended-Rydberg parameters to the Rydberg parameter, i.e. the direct approach, derivative approach and integral approach. The derivative and integral methods possess comparative advantages for small and large bond stretching, respectively. Although the direct method is generally the least accurate, a criterion for its validity has been established via reference to the integral method. These conversions allow the better description of bond-stretching energy to be reflected without drastic change in the molecular mechanics force fields.