Cumulative coordinates for approximations of high-order atomic multipole moments in aluminosilicate and aluminophosphate sieves

摘要

A scheme to obtain approximate analytical functions for the atomic distributed multipole moments of the crystallographically different atoms within aluminosilicate and aluminophosphate sieves is discussed. Respective atomic multipole moments are derived within the CRYSTAL95 ab initio periodic Hartree-Fock code with different basis sets, from minimal STO-3G to 6-21G*. In order to illustrate the possible applications, distributed analyses are carried out for various structural models from all-siliceous zeolites and aluminophosphates with ratio Al/P = I to hydrogen forms of aluminosilicates. Simple approximate forms based on charge and geometry coordinates are proposed for the high-order moments of each atom, which are further required for the calculation of the electrostatic field within the structures. The possibility to use this analytical approach to evaluate the electrostatic field within embedded cluster models is also shortly discussed. (C) 2001 John Wiley & Sons, Inc. [References: 37]