PEROVSKITE SOLID SOLUTIONS - A MONTE CARLO STUDY OF THE DEEP EARTH ANALOGUE (K, Na)MgF3
C. Tealdi1, M.Y. Lavrentiev2, C.E. Mohn3, N.L. Allan4
1University of Pavia, Viale Taramelli 16, I-27100, Pavia, Italy
2Unated Kingdom Atomic Energy Authority, Culham Science Centre, Abingdon, Oxon OX14 3DB, United Kingdom
3University of Oslo, PO Box 1033 Blindern, N-0315, Oslo, Norway
4University of Bristol, Bristol, BS8 1TS, United Kingdom
Keywords: perovskite, structural phase transitions, Monte Carlo, neighborite, parascandolaite
Abstract
Understanding the behaviour of solid solutions over wide ranges of temperature and pressure remains a major challenge to both theory and experiment. Here we report a detailed exchange Monte Carlo study using a classical ionic model of the model perovskite parascandolaite-neighborite (K,Na)MgF3 solid solution and its end-members for temperatures in the range 300-1000 K and pressures from 0-8 GPa. Full account is taken of the local environment of the individual cations, clustering and thermal effects. Properties considered include the crystal structure, phase transitions, the thermodynamics of mixing and the non-ideality of the solid solution. Clustering of the potassium ions is examined via a short-range order parameter. Where experimental data are available for comparison, agreement is very good.
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