A combined high-pressure experimental and theoretical study of the electronic band-structure of scheelite-type AWO4 (A = Ca, Sr, Ba, Pb) compounds

Abstract

The optical-absorption edge of single crystals of CaWO4, SrWO4, BaWO4, and PbWO4 has been measured under high pressure up to ~20 GPa at room temperature. From the measurements we have obtained the evolution of the band-gap energy with pressure. We found a low-pressure range (up to 7-10 GPa) where alkaline-earth tungstates present a very small Eg pressure dependence (-2.1 < dEg/dP < 8.9 meV/GPa). In contrast, in the same pressure range, PbWO4 has a pressure coefficient of -62 meV/GPa. The high-pressure range is characterized in the four compounds by an abrupt decrease of Eg followed by changes in dEg/dP. The band-gap collapse is larger than 1.2 eV in BaWO4. We also calculated the electronic-band structures and their pressure evolution. Calculations allow us to interpret experiments considering the different electronic configuration of divalent metals. Changes in the pressure evolution of Eg are correlated with the occurrence of pressure-induced phase transitions. The band structures for the low- and high-pressure phases are also reported. No metallization of any of the compounds is detected in experiments nor is predicted by calculations.

26 pages, 1 table, 6 figures

References in corpus (6)

• Pressure effects on the structural and electronic properties of ABX4 scintillating crystals
• Optical absorption of divalent metal tungstates: Correlation between the band-gap energy and the cation ionic radius
• High-pressure structural study of the scheelite tungstates CaWO4 and SrWO4
• Determination of the high-pressure crystal structure of BaWO4 and PbWO4
• Effects of high pressure on the optical absorption spectrum of scintillating PbWO4 crystals
• High-pressure effects on the optical-absorption edge of CdIn2S4, MgIn2S4, and MnIn2S4 thiospinels

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• New Pressure-Induced Polymorphic Transitions of Anhydrous Magnesium Sulfate
• First-Principles Study of InVO4 under Pressure: Phase Transitions from CrVO4- to AgMnO4-Type Structure
• Inelastic Neutron Scattering Studies of Phonon Spectra and Simulations in Tungstates, AWO4 (A = Ba, Sr, Ca and Pb)
• The high-pressure behavior of CaMoO4
• In-situ high-pressure Raman scattering studies in PbWO4 up to 48 GPa
• Inverse pressure-induced Mott transition in TiPO${}_4$