High-pressure stability, structure and compressibility of Cmcm -MgAl2O4: an ab initio study
High-pressure stability, structure and compressibility of Cmcm -MgAl2O4: an ab initio study
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Cmcm−MgAl2O4 的高压稳定性、结构和压缩性：从头算研究
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发表时间：
2001
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影响因子：
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通讯作者：
M. Catti
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文献类型：
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作者：
M. Catti
摘要对铝酸镁的高压多晶型（CaTi 2 O 4型结构，Cmcm空间群）、低压（Fd 3 <$m）尖晶石相以及MgO和Al 2 O3进行了量子力学固态计算。 一个从头算的所有电子周期计划与本地化的基础函数（高斯型原子轨道）已被使用，采用密度泛函理论的基础上LDA和B3 LYP泛函的哈密顿。在0 ~ 60 GPa压力范围内，通过最小焓结构优化，我们预测了：（1）Cmcm-MgAl_2 O_4的全晶体结构、pV状态方程和压缩系数随压力的变化;（2）MgO-Al_2 O_3-MgAl_2 O_4系相图（不包括CaFe_2O_4型Pmcn-MgAl_2 O_4），以及MgO + Al_2O_3组合中MgAl_2O_4的Fd_3 <$m和Cmcm多晶型的形成/分解反应的平衡压力。通过LDA和B3 LYP计算，预测Cmcm MgAl 2 O 4在39和57 GPa下形成，K 0分别为248（K′=3.3）和222 GPa（K′=3.8）。结果进行比较，实验数据，在可用的情况下，不同的DFT泛函的性能进行了讨论。
Abstract Quantum-mechanical solid-state calculations have been performed on the highest-pressure polymorph of magnesium aluminate (CaTi2O4-type structure, Cmcm space group), as well as on the low-pressure (Fd3¯m) spinel phase and on MgO and Al2O3. An ab initio all-electron periodic scheme with localized basis functions (Gaussian-type atomic orbitals) has been used, employing density-functional-theory Hamiltonians based on LDA and B3LYP functionals. Least-enthalpy structure optimizations in the pressure range 0 to 60 GPa have allowed us to predict: (1) the full crystal structure, the pV equation of state and the compressibility of Cmcm-MgAl2O4 as a function of pressure; (2) the phase diagram of the MgO–Al2O3–MgAl2O4 system (with exclusion of CaFe2O4-type Pmcn-MgAl2O4), and the equilibrium pressures for the reactions of formation/decomposition of the Fd3¯m and Cmcm polymorphs of MgAl2O4 from the MgO + Al2O3 assemblage. Cmcm-MgAl2O4 is predicted to form at 39 and 57 GPa by LDA and B3LYP calculations, with K0=248 (K′=3.3) and 222 GPa (K′=3.8), respectively. Results are compared to experimental data, where available, and the performance of different DFT functionals is discussed.