Fe的结构与物性及其压力效应的第一性原理计算

First-principles calculations of structures,properties and high pressures effects of Fe

采用基于密度泛函理论的平面波赝势方法,计算了Fe的几种不同晶体结构的总能量曲线,对HCP结构下晶体结构参数c/a随压强的变化关系做计算分析.能量计算精度取为0.01eV/atom.计算得出:1)零温下Fe从bcc到hcp结构的相变压强约为15GPa,与实验结果相一致;2)压强的升高会导致Fe的磁矩减小,最终破坏Fe的磁性;3)压强升高引起hcp晶体结构参数c/a缓慢增大,而在地核压强(135—360GPa)范围内,c/a取常量约1.59能够满足计算精度的要求.

In this paper, we performed first-principles calculations for iron with different crystal structures based on density-function theory, employing the pseudopotentional and plane-wave method. We set the computational precision of energy to 0.01 eV/atom and made total-energy calculations. The calculated results show that： 1 ） The bcc iron undergoes a pressure-induced phase transform to hcp structure at about 15 GPa, which is in good-agreement with the experimental values; 2） The magnetic moment decreases with increasing pressure, which demonstrates that the high pressures will destroy the magnetism of iron; 3） The ratio of lattice parameters of hcp structure, c/a, will slowly increase with the pressure increasing. When set to a constant about 1.59, the c/a value can give the energy computation precision of 0.01 eV/atom under the pressures in the earth core.