Geometrical, elastic, electronic, phonon, and optical properties of Na₃AgO₂ from first-principles calculation

In this paper, the geometrical, elastic, electronic, phonon, and optical properties of Na₃AgO₂ have been systematically studied by first-principles calculation. The results show that Na₃AgO₂ is mechanically stable and has small compressibility. Na₃AgO₂ is an indirect band-gap semiconductor with weak interatomic interaction. The bandgap calculated by HSE06 is 2.314 eV, and that calculated by GGA is 1.261 eV. For Na₃AgO₂, in the valence band near the Fermi level, the curve peaks of TDOS at −2.11 eV and −0.885 eV are primarily composed of O 2p states, which hybridize the 4 d and 4p states of Ag. The conduction band mainly consists of the 4p, 4 d, and 5s states of Ag, while hybridizing a few 2p states of O and a few 2p and 3s states of Na. As can be seen from the phonon dispersion spectrum there is no negative phonon frequency in the whole Brillouin region, indicating the structure is stable. Mulliken bond population of Na₃AgO₂ shows that O–Ag bonds have strong covalency, O–Na bonds have strong ionic properties, Na–Na bonds and Na–Ag bonds are antibonding. Na₃AgO₂ has a small reflectivity and a small absorption coefficient in the direction of (100) and (010) and has good transparency. The transparency of blue-violet light in the (001) direction is not as good as that of low-energy visible light. The obtained results lead to the conclusion that Na₃AgO₂ is a promising p-type transparent conducting material and is expected to be applied in practice.