Beyond VN: Multifunctional Tetragonal VN 2 as a Promising Ultrahard Coating and Ultraviolet–Visible Photonic Material

ABSTRACT We conducted a comprehensive first‐principles investigation of the electronic structure, photoresponse, mechanical, and thermodynamic characteristics of the newly synthesized compound tetragonal‐VN 2 using density functional theory. The calculated lattice parameters closely align with both experimental and theoretical data. Electronic structure analysis reveals that VN 2 exhibits metallic conductivity, with significant hybridization between V‐3 d and N‐2 p states, indicating strong covalent bonding. VN 2 demonstrates isotropic optical properties, with a high static dielectric constant (56.9), notable reflectivity (59% at 0 eV), and significant absorption in the ultraviolet–visible range. It is mechanically stable, exhibits a degree of elastic anisotropy, and possesses a brittle nature. VN 2 has a Vickers hardness of 26.2 GPa, approximately three times greater than that of VN, suggesting that it is suitable for use in wear‐resistant coatings and cutting tools. From a thermodynamic perspective, VN 2 is characterized by a high Debye temperature (1023.5 K) and significant lattice thermal conductivity (59.8 W·m − 1 ·K − 1 ). Its melting temperature, which exceeds 3177 K, distinguishes it as a promising candidate for applications that require extreme temperatures. These findings establish a strong foundation for the future applications of VN 2 in advanced materials science, particularly in high‐performance coatings and photonic devices.