Structural, electronic, and optical properties ofNiAl3: First-principles calculations

Abstract

We report ab initio density-functional calculations of the structural, electronic, and optical properties of ${\mathrm{NiAl}}_{3}$, using the full-potential linearized augmented plane wave method within the generalized gradient approximation to the exchange-correlation potential. The $D{0}_{11}$ structure is found to be energetically favorable over both the cubic $L{1}_{2}$ and $A15$ phases. The density of states around the Fermi energy, including a pseudogap just above it, is dominated by strongly hybridized $\mathrm{Ni}\phantom{\rule{0.3em}{0ex}}d$ and $\mathrm{Al}\phantom{\rule{0.3em}{0ex}}p$ states. We further present a fully first principles study of the optical properties of ${\mathrm{NiAl}}_{3}$, 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 $\ensuremath{\sim}16.84\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$. 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 $(\ensuremath{\lesssim}5\phantom{\rule{0.3em}{0ex}}\mathrm{eV})$, 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.