First-principles investigation of structural, electronic, optical, and mechanical properties of novel metallic ternary halides K3XBr6 (X = Sc, Y)

Abstract

This study investigates the structural, electronic, optical, and mechanical properties of novel ternary halide compounds K3XBr6 (X = Sc, Y) using the FP-LAPW method within the WIEN2k framework. Structural analysis confirms their cubic symmetry, with optimized lattice parameters obtained via the Birch-Murnaghan equation of state, indicating greater structural stability for K3YBr6 compared to K3ScBr6. The calculated formation energies of − 1.325 eV/atom for K3ScBr6 and − 2.012 eV/atom for K3YBr6 confirm their thermodynamic stability. Furthermore, the absence of imaginary frequencies in the phonon dispersion spectra verifies their dynamic (phonon) stability. Electronic calculations reveal that both compounds exhibit metallic behavior, with overlapping valence and conduction bands. K3ScBr6 demonstrates higher carrier mobility, while K3YBr6 offers a better overall balance of physical and electronic characteristics. The valence band structure is predominantly shaped by bromine p-orbital contributions, which play a central role in the electronic behavior. Optical analysis highlights their potential in optoelectronic applications such as lasers, solar cells, and plasmonic devices, with K3ScBr6 optimized for ultraviolet response and K3YBr6 covering both ultraviolet and visible regions. Mechanical evaluation shows that K3ScBr6 is harder, stiffer, and more brittle, whereas K3YBr6 is softer, more ductile, and exhibits higher metallicity. These results position K3XBr6 (X = Sc, Y) as promising candidates for next-generation electronic, optoelectronic, and photonic technologies.

Keywords

• FP-LAPW method
• Wien2K
• Structural stability
• Mechanical Stability
• Optoelectronic Properties