Atomic mechanisms of superionic conductivity in fluorite

The subsequent melting/crystallization of the two sub-lattices of CaF2 is explored by molecular dynamics simulations. Both, heating from 100 K and cooling from 2500 K encompasses two transitions, i.e. the melting/recrystallization of the fluoride sub-lattice and the of whole crystal at different temperatures. Solid state F- ion conductivity is observed in a temperature range of about 1500-2000 K which reflects a reasonable agreement with the experiment. A systematic study of fluoride migration revealed the atomistic mechanisms of the spontaneous formation of Frenkel defects, followed by void translocation and terminated by recombination of interstitial fluoride ions and vacancies. (C) 2008 Elsevier B.V. All rights reserved.