Structural, electronic, and optical properties of NiAl3: First-principles calculations

We report ab initio density-functional calculations of the structural, electronic, and optical properties of NiAl3, using the full-potential linearized augmented plane wave method within the generalized gradient approximation to the exchange-correlation potential. The D 011 structure is found to be energetically favorable over both the cubic L 12 and A15 phases. The density of states around the Fermi energy, including a pseudogap just above it, is dominated by strongly hybridized Ni d and Al p states. We further present a fully first principles study of the optical properties of NiAl3, using the long wavelength random phase approximation expression for the dielectric function obtained within linear response theory, with full matrix elements. Our calculations cover a large frequency range, extending previous theoretical studies to energies going up to and beyond the effective plasma frequency, which we calculate to be ∼16.84 eV. Our results are analyzed in the light of the calculated electronic band structure and density of states, and compared with experimental findings. In the low energy range (5 eV), where data from different experimental techniques coincide, the calculated reflectivity reproduces very well the main features observed. At higher frequencies, we find a Drude-like behavior, dressed by interband transitions. Our findings invite future measurements that will allow a fuller comparison between theory and experiments.