Investigation of electronic structure and anisotropy of the Lamb-Mössbauer factor in ZnF2 single crystals

Abstract

Using the 93.3 keV resonance in67Zn the isomer shift, the quadrupole interaction, and the anisotropy of the Lamb-Mossbauer factor (LMF) in ZnF2 single crystals have been investigated. The main component of the electric field gradient (efg) tensorVzz=+(2.18+-0.22)×1017V/cm2 andη=0.29±0.03 are derived.Vzz is oriented perpendicular to the crystallographicc axis. The anisotropy of the LMF is large:fx=(2.4±0.1)%,fy=(2.3±0.2)%, andfz=(1.4±0.2)%. Ab initio Hartree-Fock cluster calculations gave a detailed description of the observed charge distribution including the orientation of the efg tensor. Using a force constant model (shell model), we solved the eigenvalue problem of the dynamic matrix and quantitatively reproduced the anisotropy of the LMF.