Lower order atomic multipole moments of the oxygen atoms of “small size” H-form aluminosilicate frameworks

Abstract

The geometries of all possible SiO(H)Al Brönsted centres within five hydrogen form (H-form) aluminosilicate frameworks, ABW, CAN, CHA, EDI, and NAT, were optimised using a full periodic ab initio Hartree–Fock LCAO scheme at the STO-3G level. A distributed multipole analysis (DMA) was then applied at the ps-21G ∗(Al, Si)/6-21G ∗(O, H) level in order to obtain the multipole moments. Simple analytical approximations of the dependence of the Mulliken charges and atomic dipole moments with respect to the average bond distance, the anisotropy between the AlO and SiO distances, and the SiOAl angle for all crystallographically independent types of oxygen atom were derived on the basis of all optimised models. The nuclear quadrupole coupling constants for 17O are calculated for all oxygen positions and compared to the experimental values measured for zeolites A, LSX, and Y.