Electrostatic potential and field approximation for aluminosilicates in cation-substituted forms

Water molecules were removed from the X-ray structure models of zeolites with comparatively small-sized unit cells (BIK, BRE, EDI, GIS, GOO, LAU, and PHI), and cations were replaced by cations of only one type (Mg or Zn). The dehydrated zeolite models obtained were optimized with the Bush and Catlow force fields. The dependences of atomic multipole moments up to the fourth order along the so-called cumulative coordinate were calculated for these models by the density functional method with periodic boundary conditions. These dependences were used to estimate the electrostatic potential and electric field in the cross section of a zeolite that was not used to calculate them. The data obtained with atomic charges borrowed directly from calculation results were quite satisfactory.