First‐Principles Investigation of the Electronic, Phonon, Optical, and Elastic Properties of AgBiTeSe

ABSTRACT AgBiTeSe, a quaternary chalcogenide compound, is emerging as a promising candidate for advanced thermoelectric, optoelectronic, and photonic applications due to its exceptional electronic, optical, and mechanical properties. Using first‐principles calculations within the density functional theory (DFT) framework, we investigate the material's electronic structure, phonon dynamics, optical response, and mechanical characteristics. The electronic band structure reveals metallic behavior with high carrier mobility, characterized by multiple dispersive bands crossing the Fermi level and strong hybridization between Bi‐p, Se‐p, Te‐p, and Ag‐d states. Phonon dispersion extends up to 7 THz, showing imaginary modes near the G and M points, indicating potential dynamic instability in the pristine structure, which can be stabilized via doping, alloying, or external pressure. Optically, AgBiTeSe demonstrates significant absorption (up to 2.5 × 10 5 cm − 1 ) in the UV–visible range (8–12 eV), a high static dielectric constant (∼200), and a plasmon resonance peak near 18–20 eV. Mechanical analysis confirms ductility (B/G > 1.75) and notable anisotropy, with elastic constants satisfying the Born‐Huang stability criteria. These findings position AgBiTeSe as a multifunctional material combining high electrical conductivity, efficient light‐matter interaction, and favorable thermomechanical properties, making it a strong candidate for next‐generation thermoelectric, optoelectronic, and plasmonic applications.