Department of Physics, Nanyang Normal University, Nanyang 473061, China.
Dalton Trans. 2012 Aug 28;41(32):9781-8. doi: 10.1039/c2dt30254c. Epub 2012 Jul 13.
A theoretical investigation on structural and thermodynamic properties of 11-type iron-based superconductor FeSe at high pressure and high temperature was performed by employing the first-principles method based on the density functional theory. Some structural parameters of FeSe in both tetragonal and hexagonal phases are reported. According to the fourth-order Birch-Murnaghan equation of states, the transition pressure P(t) of FeSe from the PbO-type phase to the NiAs-type phase was determined. The calculated results are found to be in good agreement with the available experimental data. Based on the quasi-harmonic Debye model, the pressure and temperature dependence of the thermodynamic properties for hexagonal phase FeSe were investigated. Our theoretical calculations suggest that the pressure and temperature have significant effects on the heat capacity, vibrational internal energy, vibrational entropy, vibrational Helmholtz free energy, thermal expansion coefficient and Debye temperature. Even though few theoretical reports on the structural properties of FeSe are found in the current literature, to our knowledge, this is a novel theoretical investigation on the structural and thermodynamic properties of FeSe at high temperature. We hope that the theoretical results reported here can give more insight into the structural and thermodynamic properties of other iron-based superconductors at high temperature.
采用基于密度泛函理论的第一性原理方法，对高压高温下 11 型铁基超导体 FeSe 的结构和热力学性质进行了理论研究。报道了 FeSe 在四方相和六方相中的一些结构参数。根据第四阶 Birch-Murnaghan 状态方程，确定了 FeSe 从 PbO 型相到 NiAs 型相的转变压力 P(t)。计算结果与现有实验数据吻合较好。基于准谐德拜模型，研究了六方相 FeSe 的热力学性质随压力和温度的变化。我们的理论计算表明，压力和温度对热容、振动内能、振动熵、振动亥姆霍兹自由能、热膨胀系数和德拜温度有显著影响。尽管目前文献中关于 FeSe 结构性质的理论报道很少，但据我们所知，这是对高温下 FeSe 的结构和热力学性质的一项新的理论研究。我们希望这里报道的理论结果能为高温下其他铁基超导体的结构和热力学性质提供更多的认识。
