Structural, electronic, and optical properties of three types CaN from first-principles study.

Context: To find the potential value of CaN in the field of optoelectronics, the physical properties of CaN will be analyzed. It can be concluded from the electronic properties that the Ca-N bonds of α-CaN are more stable than those of δ-CaN and ε-CaN. The dielectric function, reflectivity function, and absorption function of three types of CaN were accurately calculated, and it was concluded that α-CaN, δ-Ca3N, and ε-CaN have greater transmittance for visible light and exhibit optical transparency in the near-infrared frequency domain. Combined with the high hardness, strong bonding, high melting point, and wear resistance of CaN, Ca3N can be used as a new generation of window heat-resistant materials. The α-CaN, δ-CaN, and ε-CaN are indirect, direct, and indirect narrow bandgap compounds, respectively, that is, δ-CaN is more suitable for luminescent materials than α-CaN and ε-CaN. α-CaN and δ-CaN have high reflective properties in the ultraviolet region and can be used as UV protective coatings. All three CaN materials can be used industrially to synthesize photovoltaic devices that operate in the ultraviolet region.

Methods: Based on the first-principles of density functional theory calculations, the structures, electronic properties, and optical properties of α-, δ-CaN, and ε-CaN were calculated. The calculation results show that although the α-CaN, δ-CaN, and ε-CaN have similar electronic structures, some phases have better properties in some aspects.