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The Full Potential-Linearized Augmented Plane Wave (FP-LAPW) is employed into density functional theory (DFT) within WIEN2k package to explore and investigate the thermoelectric, mechanical, electronic and structural properties of full-Heusler alloys Li2BeX (X = Si, Ge and Sn) were explored. The exchange and correlation potential are treated by different approximations: the generalized gradient approximation with Perdew–Burke–Ernzerhof scheme (GGA-PBE) and Tran–Blaha modified Becke–Johnson (mBJ-GGA). The results achieved for the electronic properties show that these compounds are semiconductor in nature with an indirect band gap, of values: 0.60 eV, 0.55 eV and 0.24 eV for Li2BeSi, Li2BeGe and Li2BeSn, respectively. In addition, these materials are mechanically stable owing to the fact that the conditions required for this mechanical stability satisfy Born’s criteria, and are of a brittle nature due to the calculated values of the ratios (B/G), on the other hand, these compounds are dynamically stable due to the non-presence of negative frequencies following the detailed study of phonons. These compounds are characterized by a high figure of merit (ZT) (close to unity) and high Seebeck coefficient (S), making them promising candidates for thermoelectric applications.

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The structural, elastic, mechanical, magneto-electronic, and thermoelectric properties of Sr2TiCoO6 double perovskite oxide have been studied within the framework of density functional theory. The FP-LAPW method within the (GGA) and (mBJ) approximations is chosen in the computational approach. This alloy crystallizes in cubic structure with the ferromagnetic phase. The computed lattice constant was found to agree with the available experimental results. This compound shows the half-metallic ferromagnetic properties. A value of 1 µB is found for the total magnetic moment with an important contribution from Co atoms. The elastic parameters reveal that Sr2TiCoO6 as being super hard and brittle. We calculated the thermoelectric properties of Sr2TiCoO6 using the Boltzmann transport equations within the DFT in a temperature range from 100 to 1000 K. The transport parameters like Seebeck coefficient, electrical thermal conductivity and the merit factor, have been put together to establish their thermoelectric response. The figure of merit value is between [0.71-0.99] indicating that our compound is a good candidate for thermoelectric applications at high and low temperatures.

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