Electronic densities of states of several intermetallic compounds with large coordination numbers calculated within the framework of band theory

摘要

The electronic densities of states of intermetallic compounds with the following types of structures are discussed within the framework of band theory with special interest in the possibility of their use for thermoelectric materials (TEMs) with low lattice heat conductivities: NaZn_(13)-, BaCd_(11)-, Mn_(12)Th-, Ni_(17)Th_2-, Zn_(17)Th_2-, and CaCu_5-type structures. Semiconducting materials, which are considered to be favorable for TEMs, could not be found from the compounds which were investigated. However, RZn_(12) (R: heavier rare earth (RE) metal) and R'Zn_(11) (R': lighter RE metal) can be the candidates for the n-type and p-type TEMs, respectively, if Mott's theory for the Seebeck coefficients of 3d metals is valid for f metal compounds and the positions of f band are supposed to be evaluated precisely by band-calculation. YbZn_(13) and YbNi_5 are promising if the direct contribution of the 4f electrons to the conduction can be expected as in the case of YbAl_3, which is supposed to be caused by upward shift of the 4f energy levels due to the strong correlation of the 4f electrons. LaCo_(13) and Co_(17)Y_2 are interesting if an enhanced ferromagnetism cause the increase in Seebeck coefficient.