First-principles simulation of high-pressure polymorphs in MgAl2O4
First-principles simulation of high-pressure polymorphs in MgAl2O4
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DOI：
10.1007/s00269-008-0231-9
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发表时间：
2008-04
影响因子：
1.4
通讯作者：
S. Ono;S. Ono;J. Brodholt;G. D. Price
中科院分区：
文献类型：
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作者：
S. Ono;S. Ono;J. Brodholt;G. D. Price
我们用密度泛函理论研究了MgAl_2O_4多晶型体在压力下的稳定性。我们的结果可以合理地解释在以前的实验中观察到的MgAl2O4多晶型的过渡序列。尖晶石相（在环境条件下稳定）在14 GPa下分解为方镁石和尖晶石。随着压力的增加，发生从两种氧化物到铁酸钙相的相变，并最终在68 GPa下转变为钛酸钙相。钛酸钙相是稳定的，至少150 GPa，我们没有观察到一个六方相或方镁石+ Rh2O3（II）型Al2O3的稳定场。在这项研究中计算的相的体积模量是在高压实验中测量的那些很好的协议。我们的研究结果与以前使用类似方法的研究结果不同。我们将这种不一致归因于在先前的计算中在高压下对细胞形状和离子位置的不完全优化。
We have used density functional theory to investigate the stability of MgAl2O4polymorphs under pressure. Our results can reasonably explain the transition sequence of MgAl2O4polymorphs observed in previous experiments. The spinel phase (stable at ambient conditions) dissociates into periclase and corundum at 14 GPa. With increasing pressure, a phase change from the two oxides to a calcium-ferrite phase occurs, and finally transforms to a calcium-titanate phase at 68 GPa. The calcium-titanate phase is stable up to at least 150 GPa, and we did not observe a stability field for a hexagonal phase or periclase + Rh2O3(II)-type Al2O3. The bulk moduli of the phases calculated in this study are in good agreement with those measured in high-pressure experiments. Our results differ from those of a previous study using similar methods. We attribute this inconsistency to an incomplete optimization of a cell shape and ionic positions at high pressures in the previous calculations.