非平衡分子动力学法模拟计算SiC材料的热导率
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摘要
为了探究更高效的碳化硅(SiC)材料热导率的模拟方法,应用逆非平衡分子动力学(rNEMD)法及传统非平衡分子动力学(NEMD)法对β晶型SiC(β-SiC)材料的热导率进行模拟计算和对比; 2种方法的模拟过程均先建立横截面尺度小而轴向尺度大的棒状模型,采用周期性边界条件、应用修正嵌入原子法(MEAM)势函数,先后进行正则系综(NVT)的弛豫和微正则系综(NVE)内的动态沿轴向生成温度梯度的过程,分别利用傅里叶定律模拟计算得到SiC材料的热导率。结果表明:2种方法的计算结果均出现热导率随生成温度梯度的材料轴向尺度增加而增大的有限尺度效应,应用倒数拟合的外推法可以计算模拟体系沿轴向为无穷大时的宏观体相β-SiC材料的热导率; r NEMD法具有较高的计算效率,更适合热导率的模拟计算。
In order to find a more efficient method to simulate the thermal conductivity of Si C,reverse and conventional non-equilibrium molecular dynamics method were applied to investigate the thermal conductivity of β-Si C crystal respectively. In the simulation process of the two methods,simulation cells of cross sections with small area and axial lengths with large size were constructed. Periodic boundary conditions and modified embedded atom method(MEAM) potential were adopted and canonical(NVT) ensemble for equilibrating and microcanonical(NVE) ensemble for generating temperature gradient in axial direction were implemented,then the results of thermal conductivity of β-SiC crystalachieved from the two methods were deduced from Fourier's law. The results show that the finite-size effect of both methods is observed that the thermal conductivity increases with the increasing length in axial direction. An inverse fitting method is applied and bulk thermal conductivity of β-Si C crystal can be obtained by extrapolating the size in axial direction to an infinite system size. The reverse non-equilibrium method has a more effective computational process making it more applicable for the numerical simulation of thermal conductivity.
In order to find a more efficient method to simulate the thermal conductivity of Si C,reverse and conventional non-equilibrium molecular dynamics method were applied to investigate the thermal conductivity of β-Si C crystal respectively. In the simulation process of the two methods,simulation cells of cross sections with small area and axial lengths with large size were constructed. Periodic boundary conditions and modified embedded atom method(MEAM) potential were adopted and canonical(NVT) ensemble for equilibrating and microcanonical(NVE) ensemble for generating temperature gradient in axial direction were implemented,then the results of thermal conductivity of β-SiC crystalachieved from the two methods were deduced from Fourier's law. The results show that the finite-size effect of both methods is observed that the thermal conductivity increases with the increasing length in axial direction. An inverse fitting method is applied and bulk thermal conductivity of β-Si C crystal can be obtained by extrapolating the size in axial direction to an infinite system size. The reverse non-equilibrium method has a more effective computational process making it more applicable for the numerical simulation of thermal conductivity.
引文
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[16] CROCOMBETTE J P,DUMAZER G,HOANG N Q,et al. Molecular dynamics modeling of the thermal conductivity of irradiated Si C as a function of cascade overlap[J]. Journal of Applied Physics,2007,101(2):023527.
[2] KATOH Y,SNEAD L L,HENAGER J C H,et al. Current status and recent research achievements in Si C/Si C composites[J].Journal of Nuclear Materials,2014,455(1/2/3):387-397.
[3] YUTAI K,KAZUMI O,CHUNGHAO S,et al. Continuous Si C fiber,CVI Si C matrix composites for nuclear applications:properties and irradiation effects[J]. Journal of Nuclear Materials,2014,448(1/2/3):448-476.
[4]于海蛟,周新贵,张炜,等.聚变堆结构应用SiC/SiC热导率的研究进展[J].材料导报,2010,24(2):88-92.
[5] SNEAD L L,NOZAWA T,KATOH Y B,et al. Handbook of Si C properties for fuel performance modeling[J]. Journal of Nuclear Materials,2007,371(1/2/3):329-377.
[6]张驰,梁汉琴,李寅生,等.碳化硅材料热导率计算研究进展[J].硅酸盐学报,2015,43(3):268-275.
[7] SCHELLING P K,PHILLPOT S R,KEBLINSKI P. Comparison of atomic-level simulation methods for computing thermal conductivity[J]. Physic Review:B,2002,65(14):144306.
[8] MLLER-PLATHE F. A simple nonequilibrium molecular dynamics method for calculating the thermal conductivity[J]. The Journal of Chemical Physics,1997,106(14):6082-6085.
[9]于海蛟,周新贵,张炜,等.聚变堆结构材料Si C/SiC的研究进展[J].材料导报,2009,23(12):104-108.
[10] TANG Q. A molecular dynamics simulation:the effect of finite size on the thermal conductivity in a single crystal silicon[J].Molecular Physics,2004,102(18):1959-1964.
[11] YANG Y W,LIU X J,YANG J P. Nonequilibrium molecular dynamics simulation for size effects on thermal conductivity of Si nanostructures[J]. Molecular Simulation,2008,34(1):51-55.
[12]侯泉文,曹炳阳,过增元.碳纳米管热导率的分子动力学研究[J].工程热物理学报,2009,30(7):1207-1209.
[13]魏志勇,毕可东,陈云飞.石墨烯纳米带热导率的分子动力学模拟[J].东南大学学报(自然科学版),2010,40(2):306-310.
[14] PLIMPTON S. Fast parallel algorithms for short-range molecular dynamics[J]. Journal of Computational Physics,1995,117(1):1-19.
[15] BASKES M I. Modified embedded-atom potentials for cubic materials and impurities[J]. Physical Review:B,1992,46(5):2727-2742.
[16] CROCOMBETTE J P,DUMAZER G,HOANG N Q,et al. Molecular dynamics modeling of the thermal conductivity of irradiated Si C as a function of cascade overlap[J]. Journal of Applied Physics,2007,101(2):023527.