The Effects of the Organic-Inorganic Interactions on the Thermal Transport Properties of CH3NH3PbI3
The Effects of the Organic-Inorganic Interactions on the Thermal Transport Properties of CH3NH3PbI3
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DOI：
10.1021/acs.nanolett.6b00457
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发表时间：
2016-04-01
期刊：
影响因子：
10.8
通讯作者：
Yamashita, Koichi
中科院分区：
文献类型：
--
作者：
Hata, Tomoyuki;Giorgi, Giacomo;Yamashita, Koichi
甲基碘化铅钙钛矿(CH3NH3PbI3)是目前研究最多的有机-无机杂化卤化物钙钛矿，具有较低的导热系数。甲基铵离子的旋转运动被认为是抑制声子输运的原因，然而，到目前为止，这一过程的具体机制还没有弄清楚。在这项研究中，我们基于分子动力学模拟阐明了旋转在热性质中的作用。为此，我们用从头计算方法建立了CH3NH3PbI3的经验势能，并用非平衡分子动力学方法计算了它的热导率。将结果与含有不同嵌入阳离子的模型系统进行了比较，结果表明旋转运动提供了主要的抑制作用。我们还检查了振动态密度与温度的关系，并确定了发生非简谐耦合的能量范围。通过声子色散分析，我们能够充分解释抑制机制：转动与阳离子的平移运动耦合，无机晶格振动通过平移运动耦合并相互散射。
Methylammonium lead iodide perovskite (CH3NH3PbI3), the most investigated hybrid organic-inorganic halide perovskite, is characterized by a quite low thermal conductivity. The rotational motion of methylammonium cations is considered responsible for phonon transport suppression; however, to date, the specific mechanism of the process has not been clarified. In this study, we elucidate the role of rotations in thermal properties based on molecular dynamics simulations. To do it, we developed an empirical potential for CH3NH3PbI3 by fitting to ab initio calculations and evaluated its thermal conductivity by means of nonequilibrium molecular dynamics. Results are compared with model systems that include different embedded cations, and this comparison shows a dominant suppression effect provided by rotational motions. We also checked the temperature dependence of the vibrational density of states and specified the energy range in which anharmonic couplings occur. By means of phonon dispersion analysis, we were able to fully elucidate the suppression mechanism: the rotations are coupled with translational motions of cations, via which inorganic lattice vibrations are coupled and scatter each other.