ABSTRACT
In this book chapter, we summarize some of our recent work by using density functional ab initio method to understand the TE transport mechanism and help the design of novel TE materials. Since its publication in the 1960s,1,2 ab initio method based on density functional theory (DFT) has become a powerful tool to study the electronic structures of materials, especially for their ground states. Numerous papers and textbooks can be referred to obtain basic knowledge of DFT, which will be shortly overviewed
9.1 Introduction ......................................................................................9-1 9.2 šeoretical Methods........................................................................ 9-2
9.3 Type-I Ba8MxGe46-x Clathrates with Transition Metal Cross Substitution............................................................................ 9-8
9.4 Half-Heusler Intermetallic Compounds .................................... 9-12 9.5 n-Type Filled CoSb3 Skutterudites ...............................................9-16 9.6 Concluding Remarks and Outlook ............................................. 9-20 References ................................................................................................... 9-21
in the next section. DFT o¤ers the possibility to explore the materials in variable aspects. Since total energies can be calculated very accurately within DFT, the structural properties, such as lattice parameters, internal coordinates, atomic conœgurations, and compositions can be predicted. šis is important for material design since precise structural information is the basis of understanding other microscopic and macroscopic properties. Based on a reliable crystal structure, electronic structure is also able to be calculated for understanding much functionality of materials. Although the DFT nowadays has some di²culties in dealing with some systems with strongly correlated electrons, band structures, in most cases, are accurate enough to give rational interpretation and prediction of physical properties. In TE, the electrical transport properties of materials can be directly determined by their band structures, including Seebeck coe²cients, electrical conductivities, and electronic thermal conductivities, with a few reasonable physical approximations introduced. Because electrical transport properties of a material strongly correlate with its electronic structures, such calculations can also provide useful information about optimization and design of TE materials.
