A model calculation of EFG tensor modulation in Rb₂ZnBr₄ isomorphs

Abstract

Rb₂ZnBr₄ and its isomorphs are known to exhibit displacively modulated structures in their incommensurate phases and ferrophases. Correspondingly the electrical field gradient (EFG) tensor at the site of quadrupole nucleus is also modulated. This EFG tensor can be calculated assuming the validity of the point charge model. Using the experimental data for the amplitude of the EFG tensor modulation in the incommensurate phase we have calculated the displacements of the atoms in the incommensurate structure. The results are compared to the experimentaly determined ferrophase structures of K₂ZnCl₄ and Rb₂ZnCl₄.