MODELING ELECTROSTATIC POTENTIAL FROM EXPERIMENTALLY DETERMINED CHARGE-DENSITIES .2. TOTAL POTENTIAL

Experimental electrostatic potential derived from X-ray diffraction da ta was used as a given physical property for the determination of atom ic moments. The electrostatic potential is fitted against Buckingham m oments expansion up to octupolar level. The estimation of the contribu tion of the aspherical part of the density to the electrostatic potent ial necessitates a judicious choice of the points grid around the syst em in order to get stability and reliability of the results. The net c harges obtained by the fit to the electrostatic potential on a test cr ystal of the pseudo-peptide N-acetyl-alpha,beta-dehydrophenylalanine m ethylamide are close to those derived from the electron-density refine ments. The higher moments are related to the electron-density multipol ar parameters.