A first-principles study of the structural, electronic, optical, and vibrational properties for paramagnetic half-Heusler compound TiIrBi by GGA and GGA

The structural, electronic, optical, and vibrational properties of half-Heusler compound TiIrBi have been investigated by using the Generalized Gradient Approximation (GGA) and GGA plus modified Becke and Johnson (GGA + mBJ) functional within the Density Functional Theory (DFT). The obtained formation enthalpies and energy-volume curves for the three different atomic arrangements (alpha, beta and gamma) show that gamma phase is the most energetically favorable phase. Additionally, among the paramagnetic (PM), ferromagnetic (FM), and antiferromagnetic (AFM) magnetic systems considered for the gamma-phase of this compound, the paramagnetic system is found to be the most stable. The spin-polarized electronic band calculations of the TiIrBi compound demonstrate that this material has a semiconductor nature in both the majority and minority spin channels with the direct bandgap of 0.56 and 0.87 eV using the GGA and GGA + mBJ approach, respectively. The obtained formation enthalpy and phonon dispersion curves for gamma-crystal structure of TiIrBi compound show that this material is both thermodynamically and dynamically stable. We have also examined the optical properties by computing the optical parameters such as real and imaginary parts of the dielectric function, refractive index, extinction coefficient, optical conductivity, and reflectivity of the half-Heusler compound TiIrBi in the photon energy range of 0-16 eV. The collected results indicate that the TiIrBi compound has a direct bandgap semiconductor, which makes it a convenient material for technological applications in optoelectronics