固态金属中声子热传递的分子动力学模拟研究

固态金属中的热传递是声子和自由电子共同作用的结果。自由电子引起的热导率可以通过电导率,利用Wiedemann-Franz定律得到,声子引起的热导率目前仍然不能进行实验测量,只能借助其他方法来研究。本文采用非平衡分子动力学(NEMD)方法,用镶嵌原子方法(EAM)势能模型,模拟计算了不同厚度(1.760-10.56nm)金属镍薄膜中由于声子-声子作用引起的热导率。然后根据纳米厚度金属薄膜的热导率借助关联式推到宏观尺度下由于声子-声子作用引起的热导率。结果表明,对于纳米厚度金属薄膜,由于声子-声子作用引起的热导率比块体金属镍的热导率小一个数量级;薄膜厚度越小,声子-声子作用引起的热导率越小;对于块体金属镍,由于声子-声子作用引起的热导率约占其总热导率的33.0%左右。

MOLECULAR DYNAMICS STUDY ON PHONON HEAT TRANSFER IN SOLID METALS

In solid metals, heat is transferred by electrons and phonons. The electronic contribution to the thermal conductivity can be deduced from the electrical conductivity through the use of the Wiedemann-Franz law. However, the thermal conductivity due to phonon heat transfer cannot be measured directly. The thermal conductivity due to phonon heat transfer was extrapolated from thin film results calculated using the non-equilibrium molecular dynamics (NEMD) method with the embedded-atom model (EAM). The thermal conductivity due to phonon-phonon interactions in the film was calculated for different thicknesses (from 1.760 - 10.56 nm). The results show that the thermal conductivity due to phonon-phonon interactions is dependent on the thickness in thin nickel films, and it is about one order of magnitude smaller than that of the bulk material. The ratio of the thermal conductivity due to phonon-phonon interactions to the total thermal conductivity is about 33.0% in solid bulk nickel.