Exploring Chalcogen Influence on Sc2BeX4 (X = S, Se) for Green Energy Applications Using DFT

Abstract: We present a first-principles density functional theory study of the structural, electronic, optical, and thermoelectric properties of Sc2BeX4 (X = S, Se) chalcogenides for energy applications. Both compounds are dynamically and thermodynamically stable, exhibiting negative formation energies of -2.6 eV (Sc2BeS4) and -2.2 eV (Sc2BeSe4). They feature direct band gaps of 1.8 eV and 1.2 eV, respectively, within the TB-mBJ approximation, indicating strong visible-light absorption. Optical analysis reveals high static dielectric constants (9.0 for S and 16.5 for Se), absorption peaks near 13.5 eV, and reflectivity below 30 percent. Thermoelectric calculations predict p-type conduction with Seebeck coefficients reaching 2.5e-4 V/K and electrical conductivities of 2.45e18 and 1.91e18 (Ohm m s)^-1 at 300 K. Power factors approach 1.25e11 W/K^2 m s, with a maximum dimensionless figure of merit (ZT) of 0.80 at 800 K. Calculated Debye temperatures (420 K for Sc2BeS4 and 360 K for Sc2BeSe4) imply low lattice thermal conductivity. These findings establish Sc2BeX4 chalcogenides as promising materials for photovoltaic and thermoelectric applications.