External pressure effect on the electronic, optical and thermoelectric properties of the CdY2Ch4 (Ch = S, Se) spinel compounds: Via modified Becke–Johnson (mBJ) exchange potential

Highlights: • Electronic, optical and thermoelectric properties for CdY2X4 (X = S, Se) compounds are investigated for the first time. • The electronic calculation reveals a semiconducting nature of these compounds. • Both compounds show a strong response in visible light and extreme UV regions which make them potential candidate for optoelectronic devices. • Both the CdY2S4 and CdY2Se4 compounds show attractive thermoelectric properties - Abstract: We report the results of the FP-APW + lo calculations of the structural, electronic, optical and thermo-electric properties of the CdY₂Ch₄ (Ch = S, Se) compounds under hydrostatic pressure effect. The calculated ground state properties agree well with the available experimental data. The investigated materials are semiconductors, with direct band gaps (Γ- Γ) of approximately 2.18 eV, 1.53 eV for CdY₂S₄ and CdY₂Se₄, respectively, using GGA-TB-mBJ approximations. Under external pressure up to 20 GPa, both compounds show a linear decrease of energy gaps against pressure. Moreover, our calculated optical spectra over photon energies ranging from 0 to 20 eV suggest that CdY₂Ch₄ (Ch = S, Se) spinel compounds express a strong response in the energy range between the visible light and extreme UV regions, highlighting their possible application in the optoelectronic devices. Furthermore, the calculated thermoelectric properties indicate that both the CdY₂S₄ and CdY₂Se₄ compounds show interesting thermoelectric properties.