First-principles study of elastic, electronic, thermodynamic, and thermoelectric transport properties of TaCoSn

In this paper, we have performed a comprehensive set of first-principles calculations to study elastic, electronic, thermodynamic and thermoelectric properties of TaCoSn using density functional theory (DFT). Half-heusler, TaCoSn has been found to be elastically and thermodynamically stable, ductile and hard material. The Debye temperature of TaCoSn has been found to be 375.39 K. The calculated energy bands indicate that TaCoSn is an indirect band gap semiconductor and the value of gap is 1.107 eV using PBE functional and it is 1.153 eV by TB-mBJ potentials. Such small increase of band gap by TB-mBJ potential has no significant effect on the transport properties of TaCoSn. In TaCoSn, no significant spin-orbit interaction is found. The density of states at the Fermi energy is dominated by Ta-5d and Co-3d orbitals due to strong hybridization between them. We also calculate the relaxation time and lattice thermal conductivity. The lattice thermal conductivity of TaCoSn (4.95 W/mK at 300 K) is relatively small than that of other half-heusler compounds. The maximum Seebeck coefficient at 500 K is 249.41 mu V/K. The obtained power factor (S-2 sigma/tau) at 600 K is similar to 12.5x10(11) W/msK(2). The calculated maximum figure of merit (ZT) is 0.73 at 600 K indicates that TaCoSn is a promising material for thermoelectric device applications.