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

DOI: 10.1063/1.3380848 DOI Help

Authors: J. Ruiz Fuertes (Universidad de Valencia) , S. Lopez-Moreno (CINVESTAV-Querétaro) , D. Errandonea (Universitat de València) , J. Pellicer-Porres (Universitat de València) , R. Lacomba Perales (Universitat de València) , A. Segura (Universitat de València) , P. Rodriguez-Hernandez (Universidad de La Laguna) , A. Munoz (Universidad de La Laguna) , A. H. Romero (CINVESTAV-Querétaro) , J. Gonzalez (Universidad de Cantabria)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Journal Of Applied Physics , VOL 107 (8) , PAGES 083506

State: Published (Approved)
Published: April 2010
Diamond Proposal Number(s): 683

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. X-ray diffraction experiments show that monoclinic wolframite-type MgWO(4) suffers at least two phase transitions, the first one being to a triclinic polymorph with a structure similar to that of CuWO(4) and FeMoO(4)-II. The onset of each transition is detected at 17.1 and 31 GPa. In ZnWO(4) the onset of the monoclinic-triclinic transition has been also found at 16.7 GPa. This transition does not involve any change in the atomic coordination as confirmed by x-ray absorption measurements. 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 MnWO(4), which is found to have an antiferromagnetic configuration. In addition, our study reveals details of the local-atomic compression in MgWO(4) and ZnWO(4). In particular, below the transition pressure the ZnO(6) and equivalent polyhedra tend to become more regular, whereas, the WO(6) octahedra remain almost unchanged. Fitting the pressure-volume data we obtained the equation of state for the low-pressure phase of MgWO(4) and ZnWO(4). These and previous results on MnWO(4) and CdWO(4) are compared with the calculations. The compressibility of wolframite-type tungstates is also systematically discussed. Finally Raman spectroscopy measurements and lattice dynamics calculations are presented for MgWO(4).

Subject Areas: Materials, Physics

Instruments: I15-Extreme Conditions

Other Facilities: ODE at SOLEIL

Added On: 27/04/2010 08:49

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Physics Magnetism Materials Science

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