Thermoelectric properties of TbFe2 and TbCo2 in C15- laves phase: Spin-polarized DFT+U approach

Thermoelectric properties of materials are intimately related to their electronic band structure. Combining first- and second-principles calculations, we have obtained the transport properties for the spin-up and spin-down electrons of the laves phase TbFe2 and TbCo2 compounds. The unique band structure feature and the density of states at Fermi level (EF) promote the EF to a point where carriers are in energetic proximity to these features. The non-zero density of states at EF for the spin-up (↑) and spin-down (↓) electrons leads to unusual transport properties because both the (↑) and (↓) densities contributes to the states at EF. The parabolic bands in the vicinity of EF enhance the carriers mobility and hence the transport properties of TbFe2 and TbCo2. Calculations show that the spin-up/down transport coefficients are temperature-dependent. It has been found that TbCo2 possess larger Seebeck coefficient than that of TbFe2 and hence the power factor. The calculated Seebeck coefficient of TbCo2 agree well with the available experimental data.