First-principles calculations of the properties of CsXO2 materials (X = Cu, Ag and Au) in orthorhombic phase

The structural, electronic, optical, and elastic properties of CsXO₂ (X = Cu, Ag, Au) compounds have been systematically studied using first-principles density functional theory. These materials crystallize in an orthorhombic structure with space group Cmcm (No. 63), and their lattice parameters (a, b, and c) increase progressively from Cu to Au, influenced by the X atomic size. Elastic constant calculations confirm their mechanical stability, with Pugh’s ratio (B/G) identifying these compounds as ductile. Electronic structure analysis reveals that CsXO₂ compounds exhibit indirect semiconducting behavior, with conduction band minima located at the T point and valence band maxima at the Γ point in the Brillouin zone. This band alignment is crucial for understanding their electronic properties and tailoring them for specific applications. The optical properties of CsXO₂ vary significantly with their electronic structures. An increase in bandgap correlates with a shift of absorption intensities to higher energies and a decrease in static dielectric constants and refractive indices. Additionally, their transparency at photon energies above 22 eV highlights their potential for applications in optoelectronics and photonics. These findings provide valuable insights into the structure-property relationships of CsXO₂ and underscore their potential for advanced technological applications.