TOPOLOGY OF ELECTRONIC DENSITIES TAKEN FROM PARAMETRIC METHODS - A PREDICTIVE TOOL

Calculations of topological properties of the Laplacian of the electro nic density function [-del(2)rho(r)] evaluated with a parametrical (CN DO) and full-electron ab initio HF methods were performed. Results for CH4, CH3Cl, CCl4, H2S, and PH3 molecules show that the use of the sym metrical transformation to the basis set is adequate to build the CNDO electronic density functions that reproduce, in a qualitative way, th e topology of -del(2)rho(r) obtained from full-electron ab initio calc ulations. The topology of -del(2)rho(spin)(r) was evaluated using CNDO calculations. An analysis of the critical points was carried out on m odeled catalysts (Ni-5 and Mo3S14H4 clusters) to study the adsorption of C on Ni-5 and dissociation of H-2 on Mo3S14H4. The location of crit ical points was associated with the most reactive sites on the cluster surface and used to predict the C adsorption path and the most conven ient orientation of H-2 for dissociation. (C) 1998 John Wiley & Sons, Inc.