A systematic theoretical study is presented for the electronic, mechanical, and optical properties of cubic Ti3N4, Zr3N4, and Hf3N4 with the Th3P4 structure in the framework of density functional theory. The calculated band structures of Ti3N4, Zr3N4, and Hf3N4 show the indirect band gaps of 0.268, 0.909, and 1.00eV, respectively. Furthermore, the optical properties for all three materials were calculated and analyzed in detail. The calculated results are well consistent with available experimental data. Also, it is shown that all these materials have relatively large static dielectric constants at zero frequency, rendering them potential applications in microelectronic devices.

Using first-principles calculation based on density functional theory, diffusion of Mg atom into α- and β-Sn was investigated. The diffusion barriers are 0.395 and 0.435 eV for an isolated Mg atom in the α- and β-Sn, respectively. However, the diffusion barriers of the Mg atom decrease in the α-Sn, whereas they increase in the β-Sn, when an additional Mg atom was inserted near the original diffusing Mg atom, which is mainly due to strong binding of Mg-Mg atoms in the β-Sn. Therefore, it is better to use the α-Sn, rather than the β-Sn, as an anode material for Mg ion batteries.

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