Eur. Phys. J. B 50, 521-526 (2006)
https://doi.org/10.1140/epjb/e2006-00179-8

Theoretical calculations of the high-pressure phases of ZnF₂ and CdF₂

Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing, 100049, P.R. China

Corresponding author: ^a wuzy@ihep.ac.cn

Received: 27 November 2005
Published online: 17 May 2006

Abstract

First-principles calculations based on density functional theory were used to study the high-pressure phases of both ZnF₂ and CdF₂. We found that the sequence of the pressure-induced phase transitions is: Rutile (P4₂/mnm) ↦ CaCl₂ (Pnnm) ↦ PdF₂ (Pa-3) and CaF₂ (Fm3m) ↦ PbCl₂ (Pnma) ↦ Ni₂In (P6₃/mmc) for ZnF₂ and CdF₂ respectively. In ZnF₂ the behavior of the ground-state total energy, of the Gibbs free energy and of the lattice constant vs. pressure shown that the phase transition at 4 GPa from the rutile-type phase to the CaCl₂-type phase is a second-order phase transition. The mechanism of the structural change was also revealed by the transition from the PbCl₂-type phase to the Ni₂In-type phase in CdF₂. Moreover, the high-pressure behavior of divalent metal fluorides was compared and discussed.