Giri Ashutosh, Hopkins Patrick E
Department of Mechanical and Aerospace Engineering, University of Virginia , Charlottesville, Virginia 22904, United States.
J Phys Chem Lett. 2017 May 18;8(10):2153-2157. doi: 10.1021/acs.jpclett.7b00609. Epub 2017 Apr 28.
We investigate the heat transport mechanisms responsible in driving the characteristic temperature-dependent thermal conductivities of C and PCBM crystals via molecular dynamics simulations. We find that the thermal conductivity of PCBM is "ultralow" across the temperature range studied in this work. In contrast, the temperature-dependent thermal conductivity of C crystals exhibits two regimes: "crystal-like" behavior at low temperatures where thermal conductivity increases rapidly with decreasing temperature and temperature-independent thermal conductivities at higher temperatures. The spectral contributions to thermal conductivity for C suggest that the majority of heat is carried by modes in the low-frequency regime (<2 THz), which is a consequence of intermolecular interactions. Unlike for C, these modes are not responsible for heat conduction in PCBM due to the mismatch in density of states introduced by the addition of low-frequency modes from the alkyl chains that are attached to the fullerene moieties.
我们通过分子动力学模拟研究了驱动C和PCBM晶体特征性温度依赖性热导率的热传输机制。我们发现，在本工作研究的温度范围内，PCBM的热导率“超低”。相比之下，C晶体的温度依赖性热导率呈现出两种状态：低温下的“类晶体”行为，即热导率随温度降低而迅速增加，以及高温下与温度无关的热导率。对C的热导率的频谱贡献表明，大部分热量由低频区域（<2太赫兹）的模式携带，这是分子间相互作用导致的结果。与C不同，由于富勒烯部分连接的烷基链引入的低频模式导致态密度不匹配，这些模式在PCBM中并不负责热传导。
