High-pressure phase transitions and compressibility of wolframite-type tungstates

Abstract

This paper reports an investigation on the phase diagram and compressibility of wolframite-type tungstates by means of x-ray powder diffraction and absorption in a diamond-anvil cell and ab initio calculations. The diffraction experiments show that monoclinic wolframite-type MgWO4 suffers at least two phase transitions, the first one being to a triclinic polymorph with a structure similar to that of CuWO4 and FeMoO4-II. The onset of each transition is detected at 17.1 and 31 GPa. In ZnWO4 the onset of the monoclinic-triclinic transition has been also found at 15.1 GPa. These findings are supported by density-functional theory calculations, which predict the occurrence of additional transitions upon further compression. Calculations have been also performed for wolframite-type MnWO4, which is found to have an antiferromagnetic configuration. In addition, x-ray absorption and diffraction experiments as well as calculations reveal details of the local-atomic compression in the studied compounds. In particular, below the transition pressure the ZnO6 and equivalent polyhedra tend to become more regular, whereas the WO6 octahedra remain almost unchanged. Fitting the pressure-volume data we obtained the equation of state for the low-pressure phase of MgWO4 and ZnWO4. These and previous results on MnWO4 and CdWO4 are compared with the calculations, being the compressibility of wolframite-type tungstates systematically discussed. Finally Raman spectroscopy measurements and lattice dynamics calculations are presented for MgWO4.

36 pages, 12 figures, 5 tables

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• Pressure-induced alpha-to-omega transition in titanium metal: A systematic study of the effects of uniaxial stress
• Pressure effects on the structural and electronic properties of ABX4 scintillating crystals
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• High-pressure structural study of the scheelite tungstates CaWO4 and SrWO4
• High-pressure x-ray diffraction study of SrMoO4 and pressure-induced structural changes
• Combined Raman scattering and ab initio investigation of pressure-induced structural phase transitions in the scintillator ZnWO4
• Effects of high pressure on the optical absorption spectrum of scintillating PbWO4 crystals
• Experimental and theoretical investigations on ThGeO4 at high pressure

Cited by in corpus (12)

• High-pressure Raman spectroscopy and lattice-dynamics calculations on scintillating MgWO4: A comparison with isomorphic compounds
• High-pressure structural phase transitions in CuWO4
• Experimental and theoretical study of structural properties and phase transitions in YAsO4 and YCrO4
• Pressure-induced phase transition and bandgap collapse in the wide-bandgap semiconductor InTaO4
• High-pressure x-ray diffraction study of bulk and nanocrystalline PbMoO4
• Optical and structural study of the pressure-induced phase transition of CdWO${}_4$
• First-Principles Study of InVO4 under Pressure: Phase Transitions from CrVO4- to AgMnO4-Type Structure
• Room-temperature vibrational properties of multiferroic MnWO4 under quasi-hydrostatic compression up to 39 GPa
• Infrared-active phonon modes in monoclinic multiferroic MnWO4
• Pressure-induced phase transitions in AgClO4
• Peculiarities of the local structure in new medium- and high-entropy, low-symmetry tungstates
• Identification of the high-pressure phases of alpha-SnWO4 combining x-ray diffraction and crystal structure prediction