High-pressure structural phase transitions in magnesium fluoride studied by electronic structure calculations

Abstract

The present work employs the self-consistent tight binding linear muffin tin orbital method (TB-LMTO) to calculate the electronic structure and the relative stability of MgF2. MgF2 is found to undergo a series of structural phase transitions under high pressure. The sequence of the structural phase transition is rutile→CaCl2→PdF2→ cotunnite that occurs around 10, 14.1 and 36.8 GPa, respectively. The calculated transition pressures are in fairly good agreement with the experimental results. The ground state properties of this compound are calculated in all the phases. The band structures are plotted at ambient as well as at high pressures. This compound is a wide band gap insulator with a gap of 6.45 eV at ambient conditions. The band gap tends to increase continuously even in the final high-pressure phase in contrast to other alkaline earth fluorides [45,46] wherein metallisation has been predicted for CaF2, SrF2 and BaF2. The possible reason for this behaviour in MgF2 is also discussed. © 2002 Elsevier Science B.V. All rights reserved.