First Principles Study Of Thermoelectric Materials With Low Thermal Conductivity

Several typical thermoelectric materials with low thermal conductivity, such as Ba8T16P30( T = Cu, Au) clathrate, ATSb( A = Li, Cs, T = Zn, Cd) and In4X3( X = Se, Te) were studied with first principles based on density functional theory. We calculated the electronic and thermoelectric properties of the materials with two different exchange potentials. The obtained results were compared with the experimental ones. By the comparison, we could determine the carrier concentration of the compounds. Our studies supply important proof for optimization of their thermoelectric properties. Our main results are summarized as follows.(1) The electronic and thermoelectric properties of Ba8T16P30(T = Cu, Au) were calculated by first principles for the first time. It is found that Ba8Cu16P30 and Ba8Au16P30 are both p-type semiconductor. We discuss the Band of Ba8Cu16P30 and Ba8Cu16P30 and found that Ba8Cu16P30 belongs to the direct band semiconductor while Ba8Au16P30 belongs to indirect band gap semiconductor. Our calculated transport properties of the compounds are in good agreement with the experimental results.(2) It is found that both of LiCdSb and Cs ZnSb are more stable than LiZn Sb after optimizing their crystal structures of ATSb(A = Li, Cs, T = Zn, Cd). The existence of the two new compounds LiCdSb and CsZnSb was theoretically predicated for the first time. Our calculations suggest that LiCdSb is a semiconductor while CsZnSb shows metallic behaviors.(3) By the use of modified Becke-Jonson(mBJ) Exchange potential, electronic structures and Seebeck coefficient of In4Se3 and In4Te3 were calculated. The various experimental results for temperature dependent thermoelectric power of In4Se3 and In4Te3 were reproduced well by the calculations with m BJ potential. It is suggested that the discrepancy among different experiments mainly originates from the variation of carrier concentration caused by different methods for sample preparation.