Unraveling lead-free Fr-based perovskites FrQCl3 (Q = Ca, Sr) and their pressure induced physical properties: DFT analysis for advancing optoelectronic performance

Abstract

A comprehensive study of structural, electronic, elastic, and optical properties of the cubic FrQCl 3 (Q = Ca, Sr) perovskite under pressure 0 − 105 GPa has been considered. Interestingly, FrCaCl 3 experiences a shift from an indirect to a direct bandgap material at 12 GPa, while FrSrCl 3 undergoes the same shift at 10 GPa, rendering these materials more advantageous for application in optoelectronic devices. As pressure rises, the electronic density of states increases near the Fermi level by shifting valence band electrons upward. This leads to a reduction in the bandgap and a shift of the bandgap from the ultraviolet to the visible region. The examination of mechanical properties indicates that FrQCl 3 (Q = Ca, Sr) perovskite exhibits significant potential for uses requiring a combination of anisotropic, and ductile behavior. Optical property analysis reveals that with an increase in hydrostatic pressure, dielectric constant's peak of both material shift towards lower photon energy area. • Structural, electronic, mechanical and optical aspects of FrQCl 3 (Q = Ca, Sr) have been calculated. • As pressure rises, the values of the v and B/G have increased, suggesting the ductility of FrQCl 3 (Q = Ca, Sr). • A transformation from an indirect (R − Γ) to a direct gap (Γ − Γ) takes place in FrQCl 3 (Q = Ca, Sr), at 12 GPa and 10 GPa. • Mechanical stability of FrQCl 3 (Q = Ca, Sr) is maintained under all applied pressures as confirmed by Born stability criteria. • Debye temperature of both investigated compounds rises with increasing pressure.