1 College of Science, Henan University of Technology, Zhengzhou 450001, China; 2 Institute of Modern Physics, Northwest University, Xi'an 710069, China
Abstract The structural, elastic, electronic, and thermodynamic properties of thermoelectric material MgAgSb in γ, β, α phases are studied with first-principles calculations based on density functional theory. The optimized lattice constants accord well with the experimental data. According to the calculated total energy of the three phases, the phase transition order is determined from α to γ phase with cooling, which is in agreement with the experimental result. The physical properties such as elastic constants, bulk modulus, shear modulus, Young's modulus, Poisson's ratio, and anisotropy factor are also discussed and analyzed, which indicates that the three structures are mechanically stable and each has a ductile feature. The Debye temperature is deduced from the elastic properties. The total density of states (TDOS) and partial density of states (PDOS) of the three phases are investigated. The TDOS results show that the γ phase is most stable with a pseudogap near the Fermi level, and the PDOS analysis indicates that the conduction band of the three phases is composed mostly of Mg-3s, Ag-4d, and Sb-5p. In addition, the changes of the free energy, entropy, specific heat, thermal expansion of γ-MgAgSb with temperature are obtained successfully. The obtained results above are important parameters for further experimental and theoretical tuning of doped MgAgSb as a thermoelectric material at high temperature.
Fund: Project supported by the National Natural Science Foundation of China (Grant No. 11504088), the Fund from Henan University of Technology, China (Grant Nos. 2014YWQN08 and 2013JCYJ12), the Natural Science Fund from the Henan Provincial Education Department, China (Grant No. 16A140027), the Natural Science Foundation of Shaanxi Province of China (Grant Nos. 2013JQ1018 and 15JK1759), and the Science Foundation of Northwest University of China (Grant No. 14NW23).
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