Exploration of the structural, optoelectronic, magnetic, elastic, vibrational, and thermodynamic properties of molybdenum-based chalcogenides A₂MoSe₄ (A =Li, K) for photovoltaics and spintronics applications: a first-principle study

Context: In the present work, the cubic phase of the chalcogenide materials, i.e., A₂MoSe₄ (A =Li, K) is examined to explore the structural, optoelectronic, magnetic, mechanical, vibrational, and thermodynamic properties. The lattice parameters for Li₂MoSe₄ are found to be a= 7.62 Å with lattice angles of α=β=γ=90° whereas for K₂MoSe₄, a= 8.43 Å, and α=β=γ=90°. These materials are categorized as semiconductors because Li₂MoSe₄ and K₂MoSe₄ exhibit direct energy band gap worth 1.32 eV and 1.61 eV, respectively through HSE06 functional. The optical analysis has declared them efficient materials for optoelectronic applications because both materials are found to be effective absorbers of ultraviolet radiations. These materials are noticed to be brittle while possessing anisotropic behavior for various mechanical applications. The vibrational properties are explored to check the thermal stability of the materials. On the basis of thermodynamics and heat capacity response, Li₂MoSe₄ is more stable than K₂MoSe₄. The results of our study lay the groundwork for future research on the physical characteristics of ternary transition metal chalcogenides (TMC). Methods: These physical properties are explored for the first time while using a first-principles approach based on density functional theory (DFT) in the framework of Cambridge Serial Total Energy Package (CASTEP) by Perdew-Burke-Ernzerhof generalized gradient approximation (PBE-GGA) functional. However, GGA+U and HSE06 are also employed to improve electronic properties. Kramers–Kronig relations are used to evaluate the dielectric function with a smearing value of 0.5 eV. Voigt-Reuss-Hill approximation is used for seeking the elastic response of these materials. The thermodynamic response is sought by harmonic approximation. The density functional perturbation theory (DFPT) approach is used for investigating atomic vibrations.