The Study Of Thermal Rectification In Low Dimensional Lattice System

From the end of last century, owing to the rapid development of computer technology, great progress has been made in the study of thermal conduction in low dimensional systems by computer simulation. Due to the restriction in space dimensions, low-dimensional systems exhibit different macroscopic thermal transporting properties from their three-dimensional countpart, which have wide applications in many fields. In the early study of thermal conduction in low-dimensional lattice models,it is found that the thermal conductivity increases with the system size by a power law in some systems, which is the so-called anomalous heat conduction and provides a possibility for design of(micro) small high efficient cooling components for integrated circuit, and also for the development of more efficient thermal insulation materials. In recent years, some models of nanoscale thermal device has been initially designed, such as thermal diode, heat transistor, thermal logic gate device, thermal memory and so on, which have great value in the potential applications in heat transport and thermal control as well as information processing. In the study of thermal properties of these devices, the study of properties of thermal rectification is one of the most basic ingredients. Therefore,How to effectively improve the thermal rectification of thermal device and control the heat flow turn out to be inevitable for both design and preparation of thermal devices of higher quatity. In this paper, we firstly establish two low-dimensional lattice models on how to improve and control system heat rectifying, and then we use the non-equilibrium molecular dynamics method to study the properties of thermal rectification in these low-dimensional lattice models.(1) We have studied the influence of the substrate on the thermal rectification in the low-dimensional lattice. The results show that by adjusting the chain between the substrate and the quality of the coupling coefficient can achieve low-dimensional lattice thermal rectification regulatory purposes. Since the introduction of the coupling between the chain system will generate interfacial thermal resistance between the mutual coupling of the particles, which hinders the transport of heat and results in an overall system heat flow reducing. When the ratio of the base mass and the maximum atomic mass ? is 0.5, the thermal rectification works best. While the coupling coefficient is larger, the system of hot rectification works best. More importantly, we found a suitable coefficient between substrate quality and chain coupling would have a greater thermal rectification effect with one-dimensional lattice gradient mass chains compared with no coupling of the basement. Although the total heat flow in a system decreases, but its thermal rectification factor is increasing. In addition, from the angle of the phonon mode matching, we will be able to explain this phenomenon well of thermal rectification of the model.(2) We have studied two segments of thermal rectifying properties which have quality gradient FK chain coupling system. The results show that the quality gradient chain due to the introduction of quality gradients increased interfacial thermal resistance between adjacent atoms, which hinder the spread of heat flux. In the same conditions, the heat flux is less than the uniform quality chain through the heat flow. However, with a quality of gradient chain has a better thermal rectification factor than with no quality of gradient chain. Meanwhile, we can change the relationship between the two FK chain atom interaction potential coefficients and external potential coefficient, used to improve the thermal rectification system. In addition, we can change the relationship between the two FK chain atom interaction potential coefficients and external potential coefficient in order to realize hot rectifier controlling system. Interatomic potentials coefficient for the positive and negative heat flux has a more significant impact and the system thermal rectification factor can reach about 500, which increases thermal rectification factor significantly. Coefficient of external relations for the positive impact of the heat flow is limited, but for the reverse heat is significantly influenced. By adjusting the relationship between the external potential coefficient can also achieve good heat rectifying effect. What’s more, by adjusting the coefficient of atomic interaction potential between on both ends of the chain and the relationship between the external potential coefficient, we can achieve the reversed of the heat flow. Namely, that negative heat flux from less than positive heat flux becomes greater than the positive.In order to have a better understanding of the thermal rectifier phenomenon in the model, we illustrated from the angle of phonon pattern matching.