First-principles study on electronic, vibrational, mechanical and thermodynamic properties of eight rock salt compounds

Rock salt compounds are characterized by their simple face centered cubic structure and high symmetry, making them an ideal model system for theoretical research. These compounds have a wide range of applications in high-temperature structural materials, energy storage media, geological minerals, and extreme environmental functional materials. Based on density functional theory, this study systematically investigated the basic physical properties of eight AB type rock salt compounds, including electronic, vibrational, mechanical, and thermodynamic characteristics. The results show that the energy bands of ZrC, ZrN, TiN, and HfN all pass through the Fermi level, and the conduction and valence bands overlap with each other. The bottom of the SnTe conduction band and the top of the valence band are located at the same energy position, exhibiting zero bandgap characteristics. AgBr and AgCl are medium bandgap semiconductors, while CdO is a narrow bandgap semiconductor. All eight compounds are in a mechanically and thermodynamically stable state. The mechanical properties of ZrC, ZrN, TiN, HfN, and CdO are significantly better than those of AgBr, AgCl, and CdO. The thermodynamic parameters of each compound show a significant monotonic increasing/decreasing trend with increasing temperature, and there is a close intrinsic relationship between the parameters.