Electronic and optical properties of superhard C–N materials: a first-principles study

The geometrical, electronic, and optical properties of 11 superhard C–N structures were investigated using density functional theory. The lattice parameters and energy bandgaps were calculated and compared with theoretical reports in literature. The absorption, reflectivity, refractivity, and conductivity were predicted and analyzed. It was found that only the \(\textit{Im2}\text {-CN}_{2}\) structure exhibits obvious absorption in the infrared and visible light range, whereas the other structures show no obvious absorption with small reflectivity but large refractivity in this range, indicating that these superhard C–N materials could be used for light harvesting, wear resistance, antireflection, or transparency applications depending on their structure. The various characteristics of the optical properties are explored based on the density of states (DOS) and partial DOS.