Abstract
The structural stability and physical properties of CrVO4 under compression were studied by x-ray diffraction, Raman spectroscopy, optical absorption, resistivity measurements, and ab initio calculations up to 10 GPa. High-pressure x-ray diffraction and Raman measurements show that CrVO4 undergoes a phase transition from the ambient pressure orthorhombic CrVO4-type structure (Cmcm space group, phase III) to the high-pressure monoclinic CrVO4-V phase, which is proposed to be isomorphic to the wolframite structure. Such a phase transition (CrVO4-type → wolframite), driven by pressure, also was previously observed in indium vanadate. The crystal structure of both phases and the pressure dependence in unit-cell parameters, Raman-active modes, resistivity, and electronic band gap, are reported. Vanadium atoms are sixth-fold coordinated in the wolframite phase, which is related to the collapse in the volume at the phase transition. Besides, we also observed drastic changes in the phonon spectrum, a drop of the band-gap, and a sharp decrease of resistivity. All the observed phenomena are explained with the help of first-principles calculations.
Highlights
INTRODUCTIONInteresting phenomena have been observed when pressure has been applied to this compound, including a coordination increase from 4- to 6-fold in vanadium atoms, a band-gap collapse of about 1.5 eV, which happens together with a color change, and electrical resistivity dropping at the phase transition [26][29]
Among transition metal orthovanadates of the type A3+VO4 (A = Cr, In, Fe, Tl, Al, Bi, etc.), chromium vanadate (CrVO4) is one of the prototype compounds
High-pressure X-ray diffraction and Raman measurements show that CrVO4 undergoes a phase transition from the ambient pressure orthorhombic CrVO4-type structure (Cmcm space group, phase III) to the high-pressure monoclinic CrVO4-V phase, which is isomorphic to the wolframite structure
Summary
Interesting phenomena have been observed when pressure has been applied to this compound, including a coordination increase from 4- to 6-fold in vanadium atoms, a band-gap collapse of about 1.5 eV, which happens together with a color change, and electrical resistivity dropping at the phase transition [26][29]. Motivated by these interesting phenomena and with the aim to expand the knowledge of the HP behavior of the CrVO4-type family. We report a combined experimental and theoretical study of CrVO4 under high pressure by means of X-ray diffraction (XRD), Raman spectroscopy (RS), optical-absorption measurements, resistivity characterization, and first-principles calculations. The phase transition for CrVO4 was obtained by analysing the enthalpy for the phases under study
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