Ab initio electronic structure calculations and optical properties of ordered and disordered Ni3Al

The electronic structure and optical properties of the Ni₃Al intermetallic alloy are studied by the first-principles orthogonalized linear combination of atomic orbitals method. Disordered models at different temperatures were constructed using molecular dynamics and the Vienna ab initio simulation package. The average charge transfer from Al to Ni increases steadily with temperature until the liquid phase is reached. The localization index shows the presence of relatively localized states even above the Fermi level in the disordered models. The calculated optical conductivity of the ordered phase is rich in structures and in reasonable agreement with the experimental data. The spectra of the disordered Ni₃Al models show a single broadened peak at 4.96 eV in the 0 K model which shifts towards 6.62 eV at 1400 K and then down to 5.83 eV in the liquid phase. Other results on the band structure and density of states are also discussed.