The temperature dependence of cationic disorder in Mg Al2 O4 spinel is investigated using a combination of first-principles total-energy calculations, a cluster expansion, and canonical Monte Carlo simulations. The formation energies of the possible cation-disordered structures within the spinel unit cell are predicted to be all positive, suggesting that the ground state is the normal spinel in consistency with a widely accepted view. The temperature dependence of cationic disorder is well reproduced by considering many effective cluster interactions up to quadruplets. The order-disorder transition temperature is estimated at about 860 K based on the anomaly of specific heat. The cluster expansion of the volume of Mg Al2 O4 indicates that it decreases as more cations exchange.
|ジャーナル||Physical Review B - Condensed Matter and Materials Physics|
|出版ステータス||Published - 2006 3月 23|
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