Giri Ashutosh
Department of Mechanical, Industrial and Systems Engineering, University of Rhode Island, Kingston, RI 02881, USA.
Nanoscale. 2021 Jan 21;13(2):685-691. doi: 10.1039/d0nr08776a.
Responses of materials to high pressures unveil important insight into their structure-property relationships that are otherwise masked under ambient conditions. Here, using atomistic simulations, it is shown that the thermal conductivity of methylammonium lead iodide can be drastically increased by more than an order of magnitude with applications of ∼60 GPa hydrostatic pressures. The insights gained from the molecular dynamics simulations suggest that although the inorganic constituents contribute significantly to heat flow at ambient pressure, the organic constituents are largely responsible for the drastic increase in thermal conductivity at higher pressures. The application of hydrostatic pressure leads to severe octahedral distortions resulting in higher degrees of confinement of the organic molecules and the concomitant hardening of their vibrational density of states to high frequencies encompassing a very broad spectral range that are otherwise unavailable at ambient pressure. This is shown to drastically improve the overall thermal conductivity even though the contributions from the inorganic constituents remain largely unchanged throughout the pressure range studied in this work.
材料在高压下的响应揭示了其结构与性能关系的重要见解，而这些关系在环境条件下往往被掩盖。在此，通过原子模拟表明，施加约60 GPa的静水压力可使甲基碘化铅的热导率急剧增加一个数量级以上。分子动力学模拟得出的见解表明，尽管无机成分在环境压力下对热流有显著贡献，但有机成分在更高压力下对热导率的急剧增加起主要作用。静水压力的施加导致严重的八面体畸变，从而使有机分子的限制程度更高，其振动态密度相应地硬化到高频，涵盖了在环境压力下无法获得的非常宽的光谱范围。结果表明，即使在本研究的压力范围内无机成分的贡献基本保持不变，这也能显著提高整体热导率。
