XOsSi（X=Nb，Ta）超导体的弹性、电子、热力学和输运性质：第一性原理研究
Elastic, electronic, thermodynamic and transport properties of XOsSi (X=Nb, Ta) superconductors: A first-principles exploration
摘要：
采用第一性原理计算研究了最近报道的两种锇基超导体XOsSi（X=Nb，Ta）的弹性、电子、热力学、输运和超导性质。首次计算了XOsSi的弹性常数和弹性模量。体积模量、杨氏模量和剪切模量的计算值均大于组分混合规则的平均值。NbOsSi和TaOsSi这两种化合物被发现是相对硬的材料，在性质上是弹性稳定的和可延展的。所获得的定向体积模量和剪切各向异性因子表明，两种化合物具有较高的弹性各向异性。剪切各向异性因子显示出比这些化合物的各向异性百分比更高的弹性各向异性。德拜温度和体积模量随压力增加而增加，但随温度降低，这与金属的情况相同。TaOsSi的磁化率符合居里定律，而NaOsSi由于其离域磁矩和电子比热与温度的线性关系稍有偏离而不符合居里定律。计算得到的XOsSi化合物的能带结构显示出金属性质。在这两种情况下，d轨道对总态密度都有主要贡献。较小的电子-声子耦合常数意味着XOsSi（X=Nb，Ta）是弱耦合超导体。
英文摘要：
A first-principles calculation has been performed to study elastic, electronic, thermodynamic, transport and superconducting properties of recently reported osmium based two superconductors, XOsSi (X=Nb, Ta). We have calculated elastic constants and elastic moduli of XOsSi for the first time. The calculated values of bulk, Youngs, shear moduli are reasonably larger than the average value obtained from the rule of mixtures of the constituents. NbOsSi and TaOsSi both compounds are found to be relatively hard material, elastically stable and ductile in nature. The obtained directional bulk modulus and shear anisotropic factors indicate that both compounds have high elastic anisotropy. The shear anisotropic factors show higher elastic anisotropy than the percentage anisotropy in these compounds. The Debye temperature and bulk modulus increases with pressure but decreases with temperature as usual for metals. The magnetic susceptibility of TaOsSi follow the Curie law but NaOsSi do not follow due to its delocalized magnetic moment and electronic specific heat slightly deviates from the linear relationship with temperature. The calculated band structures of XOsSi compounds show metallic nature. In both cases d-orbitals have the dominating contribution to the total density of states. The smaller electron-phonon coupling constant implies that XOsSi (X=Nb, Ta) are weakly coupled superconductors.
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