UNITED ATOM MODEL APPROACH FOR DESCRIBING C60INTERACTION ENERGY IN MOLECULAR MECHANICS

Abstract

A unified atom model for describing interaction energy between C60molecules was obtained by Liu and Wang based on the Smith–Thakkar potential function. In view of the mathematical resemblance between the Liu–Wang and the conventional Lennard-Jones (12-6) function (used in computational chemistry software for describing van der Waals energy), modified versions of the Lennard-Jones function are proposed for quantifying the potential energy between C60molecules. In this way, the Liu–Wang parameters can be converted into Lennard-Jones parameters for ready execution in commercially available computational chemistry software with minimal hard-coding involved. It was found that the Lennard-Jones function reasonably approximates the Liu–Wang model when the former's indices are increased by a factor of (7/4), without introducing any change to the coefficients. A better agreement was found when m = 4n = 35.4857, which also requires the change in repulsive and attractive indices from 1 and 2 to (1/3) and (4/3), respectively.