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arXiv 2301.10071cond-mat.mtrl-scicond-mat.stat-mech
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CsSnI3的第一性原理热力学

First-principles thermodynamics of CsSnI3

Lorenzo Monacelli, Nicola Marzari

摘要:

CsSnI3是能量收集技术的一种有前途的环保解决方案。它在室温下以黑色钙钛矿多晶型物或黄色1D双链存在,在空气中不可逆地恶化。在这项工作中,我们揭示了两种结构之间的相对热力学稳定性与CsSnI3有限温度相图的第一性原理采样,发现它是如何驱动的巨大的量子和非谐离子波动。由于非谐性的综合治疗,模拟提供了一个显着的协议与已知的实验数据的正交,菱形,立方钙钛矿结构的转变温度和热膨胀系数。我们公开了钙钛矿多晶型物是如何在\SI{270}{\kelvin}之上处于基态的,并且发现在立方黑色钙钛矿中加热时热容的异常降低。我们的研究结果也显着淡化Cs+振动模式的机械不稳定性的贡献。与实验的显着协议验证了我们的方法,它可以系统地适用于所有的金属卤化物。

英文摘要:

CsSnI3 is a promising eco-friendly solution for energy harvesting technologies. It exists at room temperature in either a black perovskite polymorph or a yellow 1D double-chain, which irreversibly deteriorates in the air. In this work, we unveil the relative thermodynamic stability between the two structures with a first-principles sampling of the CsSnI3 finite-temperature phase diagram, discovering how it is driven by anomalously large quantum and anharmonic ionic fluctuations. Thanks to a comprehensive treatment of anharmonicity, the simulations deliver a remarkable agreement with known experimental data for the transition temperatures of the orthorhombic, rhombohedral, and cubic perovskite structures and the thermal expansion coefficient. We disclose how the perovskite polymorphs are the ground state above \SI{270}{\kelvin} and discover an abnormal decrease in heat capacity upon heating in the cubic black perovskite. Our results also significantly downplay the Cs+ rattling modes' contribution to mechanical instability. The remarkable agreement with experiments validates our methodology, which can be systematically applied to all metal halides.

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