石墨烯纳米带热导率的分子动力学模拟

Thermal conductivity of graphene nanoribbons simulated by molecular dynamics

采用非平衡态分子动力学方法研究了石墨烯纳米带的热导率随温度变化的关系.通过在纳米带长度方向上施加周期性边界条件,利用Tersoff作用势和Fourier定律计算热导率.由于模拟尺寸较小时热导率随纳米带长度的增加而单调增加,为了减小长度对石墨烯纳米带热导率的影响,采用倒数拟合的方法消除了尺寸效应.模拟结果表明,石墨烯纳米带热导率随温度升高逐渐减小,这与高温下Umklapp散射作用的增强有关.结果还表明,在实际宽度近似相等的条件下,锯齿形纳米带的热导率明显高于扶手椅形,且对相同类型的纳米带,其热导率随宽度的增加而增加,表明纳米带的手性和宽度是影响石墨烯纳米带导热性能的重要参数.

The nonequilibrium molecular dynamics simulations are employed to investigate the temperature-dependent thermal conductivity of graphene nanoribbons.Periodic boundary conditions are applied along their length direction and the thermal conductivity can be deduced from Fourier law and the Tersoff potential.Since the thermal conductivity increases with the increase of the length when the simulated size is small,an inverse fitting method is employed to remove the intrinsic size effects on the simulation results.The simulations show that the thermal conductivities decrease monotonously with the increase of the temperature,which is attributed to the Umklapp scattering at high temperatures.The results also demonstrate that zig-zag nanoribbons have larger thermal conductivities compared with the arm-chair nanoribbons and the thermal conductivities for both types of nanoribbons increase with the ribbon width,indicating that the edge chirality and the width of nanoribbons are important parameters to determine the thermal property of graphene nanoribbons.