Computational and experimental investigations on structural, electronic and optical properties of scheelite compounds

Abstract

Oxide of tungstate has consistently been pursued for use in optoelectronic applications. This study details the synthesis of AWO4 (A=Ba, Sr and Ca) using a high-temperature solid-state method. Additionally, theoretical calculations highlight its electronic structure, density of states, photoelectric properties, and vibrational modes. The X-ray diffraction of AWO4 (A=Ba, Sr and Ca) was meticulously introduced by the utilization of Rietveld for refinement. The refined lattice parameters substantially verified AWO4 (A=Ba, Sr and Ca) as a tetragonal system of scheelite with the spatial group of I41/a, and demonstrated significant alteration with the discrepancy in the radius of alkaline earth metal (A-site) ions. The electronic configuration and optical attributes of AWO4 (A=Ba, Sr and Ca) possessing scheelite-like structure were explored using density functional theory (DFT) based computational techniques. The theoretical blueprint was derived by optimizing the structure based on defects. The postulated optical bandgap energy confirms the occurrence of direct electronic transitions at Brillouin region G points. Calculations suggested the direct band gaps of BaWO4, SrWO4, and CaWO4 at 4.385, 3.123 and 3.813 eV. This was attributed to the energy levels produced by O and A-site atoms in the valence band, and W and O atoms in the conduction band. An examination of the polarization effect and uneven electronic charge distribution between [CaO8]6- and [WO4]2- clusters brought about by structural defects in AWO4 (A=Ba, Sr and Ca) was performed. Moreover, advanced investigations have been conducted on the elastic constants and mechanical durability of AWO4 (A=Ba, Sr and Ca). This research extensively calculated the elastic moduli of various matrices utilizing DFT. The critical Pugh's ratio value was found to be>1.75, it indicated that AWO4 (A=Ba, Sr and Ca) has significant potential as a resilient material.