A comprehensive DFT study on the physical properties of XCrAl (X= Fe, Co, Ni, Cu) half-Heusler alloys for applications in high-temperature technology

Abstract

In the present work, structural, electronic, magnetic, elastic, mechanical, thermal and optical properties of XCrAl (X = Fe, Co, Ni, Cu) Half-Heusler (H–H) alloys were explored. First-principles study based on the non-polarized and spin-polarized density functional theory (DFT) were employed to get the geometrically relaxed unit cell structures of H–H alloys of investigation. The larger lattice constant values were found due to the spin polarization and the magnetic moments were calculated from the spin density of states (DOS). The higher values of magnetic moments make XCrAl alloys suitable for magnetic device applications. The computational electronic structure analyses at zero applied pressure confirm the zero energy band gap of XCrAl alloys which displayed metallic nature for all the compounds. From the elastic constants calculations, all the studied alloys were found mechanically and thermally stable. The values of melting temperatures were obtained in the range from 2072 to 1883 K and the calculated Debye temperatures followed the same manner of variation. Among the studied compounds, FeCrAl exhibits highest melting temperature and lattice thermal conductivity with the value of 12.94 Wm−1K−1 at 300 K which is in good agreement with the other reported results. These investigations suggest that, FeCrAl is relatively more suitable in accident-tolerant fuel (ATF) cladding material applications over the common Zr-based cladding rods. The frequency dependent optical properties of the studied H–H alloys were also explored comprehensively and the examinations indicate that, XCrAl (X = Fe, Co, Ni, Cu) alloys can also be the good choice for ultraviolet (UV) based optical device applications as they have high absorption coefficient of >200 × 104 cm−1 and maximum reflectivity of >94% in the UV region.