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arXiv 1102.5607cond-mat.mtrl-sci
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单壁氮化硼纳米管热导率的理论研究

A theoretical study of thermal conductivity in single-walled boron nitride nanotubes

Jin-Wu Jiang, Jian-Sheng Wang

摘要:

利用动力学理论对单壁氮化硼纳米管(SWBNT)的热导率进行了理论研究。通过对氮化硼片声子谱的拟合,我们发展了一个有效的、稳定的Tersoff原子间相互作用势,该势适用于sp2结构中热输运的研究。利用SWBNT对称群(线组)的螺旋量子数$(κ, n)$,我们计算出了三声子过程的选择定则。计算结果表明,热导率$κ_{\rm ph}$随长度的变化规律与$κ_{\rm ph}\propto L^β$随长度的变化规律一致,而$κ_{\rm ph}\propto L^β$随长度的变化规律与$β(T)\propto e^{-T/T_{c}}$的变化规律一致,这是边界散射与三声子散射对弯曲模的竞争作用的结果.我们发现SWBNT的两种弯曲模式对热导率的贡献占主导地位,因为它们的零频率位于$κ=\pmα$,其中$α$是SWBNT中螺旋对称的旋转角。

英文摘要:

We perform a theoretical investigation on the thermal conductivity of single-walled boron nitride nanotubes (SWBNT) using the kinetic theory. By fitting to the phonon spectrum of boron nitride sheet, we develop an efficient and stable Tersoff-derived interatomic potential which is suitable for the study of heat transport in sp2 structures. We work out the selection rules for the three-phonon process with the help of the helical quantum numbers $(κ, n)$ attributed to the symmetry group (line group) of the SWBNT. Our calculation shows that the thermal conductivity $κ_{\rm ph}$ diverges with length as $κ_{\rm ph}\propto L^β$ with exponentially decaying $β(T)\propto e^{-T/T_{c}}$, which results from the competition between boundary scattering and three-phonon scattering for flexure modes. We find that the two flexure modes of the SWBNT make dominant contribution to the thermal conductivity, because their zero frequency locates at $κ=\pmα$ where $α$ is the rotational angle of the screw symmetry in SWBNT.

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