It has been shown in experiments that applying hydrostatic pressure can enhance the thermoelectric performance of PbSe-based and SnSe-based alloys. Mg₃Sb₂ is a potential thermoelectric material with a reasonably low thermal conductivity, but its thermoelectric performance is limited by its electrical transport properties. Here, we performed density functional calculations to study the hydrostatic pressure effect on the electronic structure and the electrical transport properties of Mg₃Sb₂. The band gap of Mg₃Sb₂ exhibits a nonmonotonic change with pressure, and a band convergence with multivalley conduction states (N_V = 8) is found at 5 GPa, leading to the enhancement of the density of states (DOS) near the conduction band edge. Based on the Boltzmann transport theory, it is found that both n-type and p-type Mg₃Sb₂ have larger power factors under pressure, but the mechanisms of each are distinctly different. In n-type Mg₃Sb₂ at 5 GPa, the Seebeck coefficients along both the in-plane and out-of-plane directions clearly increase due to the increased DOS effective mass near the conduction band edge, while in p-type Mg₃Sb₂, the electron–phonon interaction near the valence band edge is suppressed under pressure, causing a smaller electronic scattering rate and a longer electronic relaxation time.

中文翻译：

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通过压力调制Mg ₃ Sb _2中的能带排列和电子-声子散射

实验表明，施加静水压力可以增强PbSe基和SnSe基合金的热电性能。Mg ₃ Sb ₂是潜在的热电材料，具有相当低的热导率，但其热电性能受到其电传输性能的限制。在这里，我们进行了密度泛函计算，以研究静水压力对Mg ₃ Sb ₂的电子结构和电传输性质的影响。Mg ₃ Sb ₂的带隙随压力呈现非单调变化，并且具有多谷导电态（N _V在5 GPa处发现= 8），导致导带边缘附近的态密度（DOS）增强。基于玻尔兹曼输运理论，发现n型和p型Mg ₃ Sb ₂在压力下均具有较大的功率因数，但两者的机理却截然不同。在5 GPa的n型Mg ₃ Sb ₂中，由于导带边缘附近的DOS有效质量增加，沿面内和面外方向的塞贝克系数明显增加，而在p型Mg _3中Sb ₂，在压力下，价带边缘附近的电子-声子相互作用受到抑制，从而导致较小的电子散射速率和较长的电子弛豫时间。