Structural stability, electronic, magnetic, elastic, thermal, thermoelectric and optical properties of L21 and xa phases of Ti2fege heusler compound: GGA and GGA+U methods

Both L21 and XA type phases ordering of Ti2FeGe compound were investigated based on density functional theory. The structural, magnetic, band structure, density of states, possibility of martensitic transformation, elastic, thermoelectric and optical properties were studied. From the calculated total energy, we noted that L21 type in ferromagnetic state is more stable phase using GGA+U approach. The computed elastic constants of considered compound show that L21 type is ductile, anisotropic and mechanically stable, while the XA phase ordering of Ti2FeGe is not mechanically stable. The (DOS) and band structure of L21 type structure of Ti2FeGe alloy show metallic character in both spin up and spin down directions, while the XA type structure exhibits half-metallic character. Based on quasi-harmonic Debye model applied in the Gibbs program, the lattice vibrational, the bulk modulus, the Debye temperature, the heat capacity, the entropy, the coefficient of thermal expansion and the Grüneisen parameter have also been estimated. The thermoelectric properties of two phases are examined and discussed through consideration of transport coefficients. The optical properties are systematically studied by computing the optical parameters. The obtained results will bring perspective for designing theoretical predictions and experimental studies intended to serve as a reference for future studies on optoelectronic and spintronic applications.