ON THE FUNCTIONAL REPRESENTATION OF BOND-ENERGY FUNCTIONS

Ab initio calculations are used to test the ability of various represe ntations to reproduce bond energies. It is found that expansion in 1/R , where R is the bond length, is remarkably efficient and is consisten tly better than the usual R expansion. A quadratic form in 1/R is bett er than a cubic representation in R and sometimes even as good as a qu artic representation. A cubic function in 1/R is, in all cases studied , better performing than the quartic expansion in R. It is also found that parameters derived with the 1/R expansion are defined more sharpl y than those derived for the R expansion. It is suggested that the 1/R expansion may be computationally more efficient for simulations of la rge biomolecules and for constructions of reactive force fields than t he standard bond functions. (C) 1994 by John Wiley and Sons, Inc.