Prediction Of Thermal Conductivity Of Low Dimensional Nanomaterialswith Non-equilibrium Molecular Dynamics Method

Low dimensional nanomaterials are key parts of nanoelectronic devices and nano electromechanical systems.The thermal conductivity of these materials is an important parameter for the design of these devices and systems.At present,the theory of microscale heat transfer is not clear,and the experimental measurement is very difficult.The molecular dynamics simulation has extraodinary advantage in predicting the thermal conductivity of low dimensional nanomaterials.First,it can be done before the results of theoretical analysis and experimental test are giwen.Second,it can consider the practical problems,such as the size of the material and the temperature of the system.Last,it can greatly reduce the investment of manpower and fund.In this paper,the molecular dynamics simulation is selected to study the thermal conductivity of low dimensional nanomaterials.The thermal conductivity of silicon thin films at room temperature(300K)was predicted by using the nonequilibrium molecular dynamics method based on the COMPASS force field.The simulation results show that the thermal conductivity of the silicon film with thickness of 4-10 nm is about 3.06-7.28W/mK,and it increases with the increase of the film thickness.The thermal conductivity of silicon thin films shows an approximately linear relationship with the thickness of the films.Phonon aerodynamic theory is employed to explain the size effect.When the film thickness decreases to tens or several nanometers,mean free path of the phonon is related to the film thickness.Carbon nanotubes are one-dimensional nano materials.They are considered as the most valuable material.Thermal conductivity of carbon nanotubes at temperature 300-900 K is predicted by molecular dynamics method.The length of the tube of carbon nanotubes is at the range of 20-40 nm.The results show that the thermal conductivity is 108.81-362.47W/mK.When temperature is same,the thermal conductivity increases with the tube length of carbon nanotubes.The finite size effect theory is applicated to discuss and analyze the results.When the tube length of carbon nanotubes is same,the thermal conductivity decreases with the rising temperature.The interaction between phonon and phonon is the main factor influencing the thermal conductivity of carbon nanotube.When the system temperature is higher,thescattering effectof the phonon turns stronger.Therefore,the thermal conductivity of carbon nanotube decreases with the increase ofthe temperature.