The Research On Thermoelectric Nanomaterials By Density Functional Theory

Recovery of low-grade energy is important in the energy conversion, pollution reduction and the environment protection. Thermoelectric conversion becomes a hot research field for its feathers of small size, light weight, no mechanical moving parts, quite working, no pollution, long life durability, and easy maintenance. Thermoelectric material is the key element in thermoelectric energy conversion system, and is the bottleneck for conversion efficient improvement. First-principles analysis in thermoelectric material can help to reveal material nature properties with few input empirical parameters. This can be helpful in the material synthesis, preparation and optimization. As nano material becomes the tendency in thermoelectric family for its versatility and flexibility, it holds the promise since the last 90 s for thermoelectric evolution. Among the nano-thermoelectric materials, the low-dimensional structures, particularly the single layer graphene and silicene show great potential.The thermoelectric properties of single layer MoS2 are studied in this thesis. After structure optimization to get the geometry parameters, the electric transport properties are calculated. The electronic conductivity, Seebeck coefficient, and electronic contribution to thermal conductivity are calculated at temperature of 300 K, 400 K and 500 K. These properties are shown in different carrier concentrations and doping types. From the comparison with other traditional thermoelectric materials, the high power factor of single layer MoS2 indicates grate promise, the material can yield appealing figure of merit as long as the thermal conductivity can be reduced. Along with the succeed art from phonon engineering, this phonon thermal conductivity can be tailed to favorable values.Empirical interatomic potential is the key part to determine thermal conductivity in molecule dynamics simulation. This is also the case when comes to single layer MoS2. We compare the home-fitted empirical potentials and several others, and try to valid one that can be used to get solid prediction for thermal properties of single layer MoS2. Results show that different potentials have their own abilities. This thesis provides the final results come from first principles and empirical potentials, and comparison of their descriptions on the geometry, mechanics properties, phonon information and thermal conductivity. One conclusion is that every potential has its specialty, a careful selection should be made with the merit of the empirical potential and the particular questions and requirements.