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首页> 外文期刊>Physical review >Hybrid density functional theory study of the high-pressure polymorphs of α-Fe_2O_3 hematite
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Hybrid density functional theory study of the high-pressure polymorphs of α-Fe_2O_3 hematite

机译：α-Fe_2O_3赤铁矿高压多晶型物的混合密度泛函理论研究

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The relative stability with respect to pressure of four structural polymorphs of Fe_2O_3 has been studied using the B3LYP hybrid exchange density functional theory, and for each polymorph a range of charge, spin, and magnetic states were examined. It was found that the B3LYP functional computed charge, magnetic ordering, structural, and elastic properties of corundum structure Fe_2O_3 are in good agreement with experiment. Magnetic ordering was found to be important for all the polymorphs, and for each polymorph antiferromagnetic ordering was found to be lower in energy than ferromagnetic ordering. The Rh_2O_3-II structure was calculated to be metastable, with the transition pressure from the corundum structure and the pressure at which magnetic collapse of Fe~(3+) cations occur in good agreement with experiment. At high pressures the lowest-energy configuration for the orthorhombic perovskite structure was computed to occur with mixed high-spin/low-spin Fe~(3+) cations. The CaIrO_3-type structure was also computed to be stable with a mixed high-spin/low-spin Fe~(3+) configuration at high pressures, and is computed to be the most stable polymorph at pressures above 46 GPa at 0 K. Overall we predict a number of phase-transition pressures which have been experimentally observed and give some insight into the mechanisms underlying the structural transformations.
机译：使用B3LYP杂化交换密度泛函理论研究了Fe_2O_3的四个结构多晶型物相对于压力的相对稳定性，并针对每种多晶型物检查了一定范围的电荷，自旋和磁态。发现刚玉结构Fe_2O_3的B3LYP功能计算电荷，磁有序性，结构和弹性性能与实验吻合良好。磁性序对所有多晶型都很重要，并且对于每个多晶型，反铁磁序的能量均低于铁磁序。 Rh_2O_3-II结构被计算为是亚稳态的，刚玉结构的转变压力和Fe〜（3+）阳离子发生磁塌陷的压力与实验吻合良好。在高压下，斜方钙钛矿结构的最低能量构型被计算为混合有高自旋/低自旋Fe〜（3+）阳离子。还计算出CaIrO_3型结构在高压下具有混合的高自旋/低自旋Fe〜（3+）构型是稳定的，并且在0 K下在46 GPa以上的压力下被计算为最稳定的多晶型物。总的来说，我们预测了已经通过实验观察到的许多相变压力，并对结构转变的潜在机理提供了一些见识。

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