Structural, electronic, and optical properties of three types Ca3N2 from first-principles study

Context: To find the potential value of Ca3N2 in the field of optoelectronics, the physical properties of Ca3N2 will be analyzed. It can be concluded from the electronic properties that the Ca-N bonds of alpha-Ca3N2 are more stable than those of delta-Ca3N2 and epsilon-Ca3N2. The dielectric function, reflectivity function, and absorption function of three types of Ca3N2 were accurately calculated, and it was concluded that alpha-Ca3N2, delta-Ca3N(2), and epsilon-Ca3N2 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 Ca3N2, Ca3N(2) can be used as a new generation of window heat-resistant materials. The alpha-Ca3N2, delta-Ca3N2, and epsilon-Ca3N2 are indirect, direct, and indirect narrow bandgap compounds, respectively, that is, delta-Ca3N2 is more suitable for luminescent materials than alpha-Ca3N2 and epsilon-Ca3N2. alpha-Ca3N2 and delta-Ca3N2 have high reflective properties in the ultraviolet region and can be used as UV protective coatings. All three Ca3N2 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 alpha-(Ca3N2), delta-Ca3N2, and epsilon-Ca3N2 were calculated. The calculation results show that although the alpha-Ca3N2, delta-Ca3N2, and epsilon-Ca3N2 have similar electronic structures, some phases have better properties in some aspects.