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A new approach to simulating disorder in crystals |
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| Authors: | I L Jones Volker Heine Maurice Leslie Geoffrey D Price |
| Institution: | 1. Cavendish Laboratory, Madingley Road, CB3 0HE, Cambridge, UK 2. SERC Daresbury Laboratory, WA4 4AD, Daresbury, Warrington, UK 3. Department of Geological Sciences, University College London, Gower Street, WC1E 6BT, London, UK |
| Abstract: | The technique of calculating lattice dissociation energies using static, minimum lattice energy, ionic models has been extended to allow for multiple occupancy of the ionic sites. A particular lattice site can have a fraction x of an ionic species A and a fraction y of an ionic species B, where the position of each can be relaxed separately along with the unit cell dimensions until an equilibrium is reached. Various degrees of long and short range order can be modelled. This technique has been applied to the mineral sillimanite, Al2SiO5, to calculate the effect on the lattice energy of (Al, Si) ordering over the tetrahedral sites. It is found using this method that (Al, Si) ordering with space group Pbmn stabilizes the material by 29.25 kcal/mol (Aliv-O-Aliv), with respect to the completely disordered material. |
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