压力驱动的结构相变解锁KMgX（X=P、As、Sb、Bi）化合物的多功能性：一项第一性原理研究
Pressure-driven structural phase transition unlocks multifunctionality in KMgX (X = P, As, Sb, and Bi) compounds: A first-principles study
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中文总结 AI 辅助
本研究通过第一性原理计算发现KMgX（X=P、As、Sb、Bi）的压力诱导正交相为稳定多功能半导体，兼具光伏与热电性能，KMgAs、KMgSb的光谱限制效率及KMgSb的zT值达到对应应用要求。
中文摘要 AI 辅助
由于多功能材料在各类能源相关器件中具有潜在应用，寻找这类材料的研究受到广泛关注。压力诱导的相变是一种无需改变材料化学成分即可获得不同结构相的有效策略，能够调控材料的物理性质并拓展其功能应用。本研究采用第一性原理计算，探究了KMgX（X=P、As、Sb、Bi）家族此前未被研究的正交（Pnma）相，确定了从四方相到正交相的压力诱导结构相变。通过物态方程分析和声子、弹性、形成焓计算，严格验证了压力可获得的正交结构的稳定性，为后续研究确立了可行性。在结合准粒子修正和激子效应的$G_0W_0$-Bethe-Salpeter方程（BSE）框架下计算的光学性质显示，其在Γ点存在偶极允许的直接跃迁，且可见光吸收系数接近$10^5\rm{cm}^{-1}$。因此，KMgAs和KMgSb在0.6μm薄膜厚度下分别达到27.12%和26.40%的光谱限制最大效率（SLME）。此外，热电输运计算预测，900K时p型和n型KMgSb的zT值分别为0.65和0.58，表明其适用于热电器件的两个支路，这些数值可能偏保守，因为Slack模型往往会高估热导率。总体而言，KMgX家族的压力可获得正交相是一种稳定的多功能半导体，兼具光伏和热电能量转换能力。
英文摘要
The search for materials with multifunctional properties has attracted significant attention due to their potential applications in various energy-related devices. Pressure-induced phase transitions provide an effective strategy for accessing different structural phases of a material without altering its chemical composition, thereby enabling the tuning of its physical properties and expanding its functional applications. In this work, we investigate the previously unexplored orthorhombic (Pnma) phase of the KMgX (X = P, As, Sb, and Bi) family using first-principles calculations and identify a pressure-induced structural transition from a tetragonal to orthorhombic phase. Stability of the pressure-accessible orthorhombic structure is rigorously confirmed by equation of state analysis together with phonon, elastic, and formation-enthalpy calculations, establishing its viability for further investigation. Optical properties calculated within the $G_0W_0$-Bethe-Salpeter equation (BSE) framework, incorporating quasiparticle corrections and excitonic effects, exhibit direct dipole-allowed transitions at the $Γ$ point and strong visible-light absorption with coefficients approaching $10^5~\text{cm}^{-1}$. Consequently, KMgAs and KMgSb achieve spectroscopic limited maximum efficiencies (SLME) of $27.12\%$ and $26.40\%$, respectively, at a thin-film thickness of $0.6~μ\text{m}$. Furthermore, thermoelectric transport calculations predict (zT) values of 0.65 and 0.58 at $900~\text{K}$ for p-type and n-type KMgSb, respectively, demonstrating its potential for both legs of thermoelectric devices. These values are likely conservative, as the Slack model tends to overestimate thermal conductivity. Overall, the pressure-accessible orthorhombic phase of the KMgX family emerges as a stable multifunctional semiconductor with coupled photovoltaic and thermoelectric energy-conversion capabilities.
