Finding optimal radial-function parameters for S atoms in the Hansen-Coppens multipole model through refinement of theoretical densities.

The multipolar model of the valence-electron-density distribution for S atoms has been optimized based on theoretical structure factors for six organic molecules. The evaluation of different sets of radial function parameters shows that: (a) the ratio of the n(l) values for different l is more important than their absolute values, as parallel changes in all n(l) for a given atom are compensated for by a change in the refined value of the kappa' parameter, and (b) the (2,4,6,8) set of n(l) with kappa' refined as a single value is an optimal choice of radial function parameters for S atoms.