Theoretical Evaluation of Multifunctional Properties of Thermodynamically Stable Dion Jacobson Family Members LiBiNb ₂ O ₇ and FrBiNb ₂ O ₇ for Optoelectronic Devices

Abstract Density functional theory (DFT) is employed by using Perdew–Burke–Ernzerhof (PBE) function in the generalized gradient approximation (GGA) framework to investigate the thermodynamic, electronic, mechanical, structural, elastic, and optical properties of the Dion Jacobson (DJ) family member (LiBiNb 2 O 7 and FrBiNb 2 O 7 ) compounds. Thermodynamic properties have been determined by using the density function perturbation theory (DFPT) technique. In thermodynamic properties of LiBiNb 2 O 7 and FrBiNb 2 O 7 , distinct zero‐point energies 1.4025 and 1.2032 eV, respectively, are computed. For both compounds at 600 K, the heat capacity (Cv) approaches the Dulong‐Petit limit values. The compounds have presented the indirect band gaps of 2.548 and 2.563 eV, respectively, indicating a semiconductor nature, which are ideal for optoelectronic applications. Highest peak values of optical conductivity (6–7 fs −1 ), absorption coefficient (10 5 cm −1 ), dielectric function (5–10), and refractive index (3–3.5) are reported in visible and near UV regions. Elastic constants are used to calculate mechanical properties, which further confirm the mechanical stability of these compounds by Born stability criteria and have predicted the ductile nature of these compounds by B/G > 1.75. Moreover, the mechanical properties show their applicability for flexible optoelectronic applications. This article provides useful information about the strategy and advancement of compounds appropriate for next‐generation solar cell devices.