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Single-crystal SnSe holds the world record for high thermoelectric performance. However, the efficiency of polycrystalline SnSe is limited due to high thermal conductivity (κ) and low electronic conductivity (σ) compared to single-crystal SnSe. Here, we report the low κ and high σ on SnSe with Si doping using semi-classical Boltzmann transport theory and first-principles calculations. Our calculated phonon dispersion curves and elastic constants of the SixSn1−xSe alloys (x varied from 0 to 0.25) show the thermodynamic and mechanical stability. Our density functional theory (DFT)-calculated elastic moduli of the α-SnSe match well with theoretical and experiment reports. The electronic properties are calculated using diversity of exchange-correlation functionals. The band gap for pristine α-SnSe is estimated to be 0.88 eV using the hybrid functional (HSE06), which is in excellent agreement with the experimental value 0.86 eV. The G0W0+Bethe–Salpeter Equation, which incorporates combined electron–electron (e–e) and electron–hole (e–h) interactions, is used to calculate the optical characteristics of pure and Si-alloyed α-SnSe. Our DFT-calculated Seebeck coefficient for SixSn1−xSe alloys for all Si doping concentrations revealed p-type behavior. At 770 K, for x = 0.25, SixSn1−xSe is found to have the lowest thermal conductivity of ~ 0.16 Wm - 1 K - 1 attributed to the high lattice anharmonicity. Our results propose a novel strategy to enhance the optical and thermoelectric properties in the SnSe-based thermoelectric materials. [ABSTRACT FROM AUTHOR]

Half-Heusler alloys are anticipated to impact real applications for instance industrial waste heat recovery due to their high thermoelectric (TE) properties, good thermal stability, and excellent elastic properties. The state-of-the-art density functional theory (DFT) is used to calculate the electronic structure, magnetic, elastic, thermodynamic, and transport properties of the cubic CrMnS half-Heusler (HH) alloy. Ferromagnetic (FM) configuration is found to be energetically most favorable than non-magnetic (NM) and antiferromagnetic (AFM) states for the HH CrMnS alloy. The spin‐resolved band structure of HH CrMnS prevails its half‐metallicity at the Fermi level with a total magnetic moment of 1 μ B . The cohesive and formation energy analysis along with the phonon dispersion curve indicate that HH CrMnS is a chemically, thermodynamically, and vibrationally stable compound. Elastic properties for the studied compound show its mechanical stability, anisotropic & brittle nature with high hardness, and Debye temperature of 410 K. Thermodynamic parameters are also calculated which depict the stability of the studied alloy at varied pressure and temperature. Furthermore, thermoelectric (TE) properties indicate that HH CrMnS alloy has a maximum value of power factor (PF) equal to 3.3 × 1011 WK−2 m−1 s−1 at 1000 K and ZT value of 0.72 at 600 K. The vibrational and mechanical stability, higher bandgap (~ 0.96 eV) and 100% spin-polarization demonstrate that HH CrMnS can be a potential alloy for TE and spintronic applications. [ABSTRACT FROM AUTHOR]

Half-Heusler (HH) alloys are a well-known and extensively researched family of thermoelectric (TE), magnetic, and spintronic materials. Doping may significantly increase the thermoelectric conversion efficiency of these materials; nevertheless, practical applications remain far. As a result, the hunt for superior parent TE alloys is critical. Using extensive first-principles density functional calculations, we predicted a novel class of vanadium-based four HH VXTe alloys, where X is one of the four elements: Cr, Mn, Fe, and Co. Their TE properties, as well as their mechanical, magnetic, electrical, and structural stability, have been studied in depth. Their mechanical and thermodynamic stability is confirmed using the predicted elastic constants, formation and cohesive energies, and phonon spectra. A comprehensive analysis of elastic constants and moduli demonstrates that HH VXTe alloys possess elastic anisotropy with reasonably good machinability, higher melting and Debye temperatures, mixed bonding characteristics with ionic and covalent contributions, and brittle nature, except for VCoTe, which is ductile. We find that the ground state of HH VCrTe and VFeTe is ferrimagnetic, while HH VCoTe is ferromagnetic and HH VMnTe is non-magnetic. Three VXTe (X = Cr, Fe, & Co) alloys demonstrated half-metallicity with 100% spin-polarization, whereas HH VMnTe is an 18-electron indirect semiconductor. In the studied HH VXTe alloys, most of the heat flow is caused by the phonon-group velocity of the acoustic phonons. Further studies on the relationship between carrier concentration and temperature dependence of TE properties reveal that the high ZT ∼1.2 at 1000 K of the pristine HH VMnTe alloy is obtained due to its high-power factor of 249.4 × 10 12 W m − 1 K − 2 and this value is greater than the values of some known pristine and doped HH TE materials. Our findings pave the way for further investigation into the HH VXTe alloys in the quest for improved TE and spintronic materials for use in domains that necessitate high thermoelectricity and spintronic performance. [ABSTRACT FROM AUTHOR]