Screened-exchange density functional theory description of the electronic structure and phase stability of the chalcopyrite materialsAgInSe2andAuInSe2

We present a systematic assessment of the structural properties, the electronic density of states, the charge densities, and the phase stabilities of ${\mathrm{AgInSe}}_{2}$ and ${\mathrm{AuInSe}}_{2}$ using screened-exchange hybrid density functional theory, and compare their properties to those of ${\mathrm{CuInSe}}_{2}$. For ${\mathrm{AgInSe}}_{2}$, hybrid density functional theory properly captures several experimentally measured properties, including the increase in the band gap and the change in the direction of the lattice distortion parameter $u$ in comparison to ${\mathrm{CuInSe}}_{2}$. While the electronic properties of ${\mathrm{AuInSe}}_{2}$ have not yet been experimentally characterized, we predict it to be a small gap ($\ensuremath{\approx}0.15$ eV) semiconductor. We also present the phase stability of ${\mathrm{AgInSe}}_{2}$ and ${\mathrm{AuInSe}}_{2}$ according to screened-exchange density functional theory, and compare the results to predictions from conventional density functional theory, results tabulated from several online materials data repositories, and experiment (when available). In comparison to conventional density functional theory, the hybrid functional predicts phase stabilities of ${\mathrm{AgInSe}}_{2}$ in better agreement with experiment: discrepancies in the calculated formation enthalpies are reduced by approximately a factor of 3, from $\ensuremath{\approx}0.20$ eV/atom to $\ensuremath{\approx}0.07$ eV/atom, similar to the improvement observed for ${\mathrm{CuInSe}}_{2}$. We further predict that ${\mathrm{AuInSe}}_{2}$ is not a stable phase, and can only be present under nonequilibrium conditions.