APPROXIMATION OF THE MOLECULAR ELECTROSTATIC POTENTIAL IN A GAUSSIAN DENSITY-FUNCTIONAL METHOD

The recently developed Asymptotic Density Model (ADM) [6, 9] is here i mplemented in the density functional framework using the program deMon -KS [13]. While the original implementation divided the atoms into a c ore shell and a valence shell, the present version allows for an arbit rary number of shells making it therefore more flexible and, as shown with benzene, potentially more accurate. Moreover, since this method i s derived through Poisson's equation, an expression for the electronic charge density is also obtained. However, the present discussion will restrict itself to the electrostatic potential. Finally, even though this method requires parametrization, it is shown that the parameters obtained for homonuclear diatomic species, and used as is in molecular calculations, yield satisfactory results. Indeed, the ADM reproduces almost all basic features of the MEP for all molecules presented here, (water, ammonia, ethylene, acetylene, hydrogen cyanide, carbon monoxi de, benzene, nitrous acid).