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The multiferroic manganese tungstate (MnWO4) has been studied by high-pressure Raman spectroscopy at room temperature under quasi-hydrostatic conditions up to 39.3 GPa. The low-pressure wolframite phase undergoes a phase transition at 25.7 GPa, a pressure around 8 GPa higher than that found in previous works, which used less hydrostatic pressure-transmitting media. The pressure dependence of the Raman active modes of both the low-and high-pressure phases is reported and discussed comparing with the results available in the literature for MnWO4 and related wolframites. A gradual pressure-induced phase transition from the low-to the high-pressure phase is suggested on the basis of the linear intensity decrease of the Raman mode with the lowest frequency up to the end of the phase transition. (C) 2014 AIP Publishing LLC. ; This work has been supported by the Spanish government under Grant No. MAT2010-21270-C04-01/04, by MALTA Consolider Ingenio 2010 Project (CSD2007-00045), by Generalitat Valenciana (GVA-ACOMP-2013-1012), and by the Vicerrectorado de Investigacion y Desarrollo of the Universidad Politecnica de Valencia (UPV2011-0914 PAID-05-11 and UPV2011-0966 PAID-06-11). We thank Professor Gospodinov, Institute of Scintillating Materials in Ukraine, for providing us high-quality MnWO INF>4 /INF> single crystals. J.R.-F. thanks the Alexander von Humboldt Foundation for a postdoctoral fellowship. A. F. acknowledges support from the Germany Research foundation within the priority program SPP1236 (Project No. FR-2491/2-1). The use of the SPP1236 central facility in Frankfurt is acknowledged. ; Ruiz-Fuertes, J.; Errandonea, D.; Gomis Hilario, O.; Friedrich, A.; Manjón Herrera, FJ. (2014). Room-temperature vibrational properties of multiferroic MnWO4 under quasi-hydrostatic compression up to 39 GPa. Journal of Applied Physics. 115(4):43510-1-43510-5. https://doi.org/10.1063/1.4863236 ; S ; 43510-1 ; 43510-5 ; 115 ; 4 ; Mikhailik, V. B., Kraus, H., Kapustyanyk, V., Panasyuk, M., Prots, Y., Tsybulskyi, V., & ...

144103-1 144103-4 85 ; S Friedrich, A., Winkler, B., Bayarjargal, L., Morgenroth, W., Juarez-Arellano, E. A., Milman, V., … Chen, K. (2010). Novel Rhenium Nitrides. Physical Review Letters, 105(8). doi:10.1103/physrevlett.105.085504 ; We have investigated by means of high-pressure x-ray diffraction the structural stability of Pd 2Mo 3N, Ni 2Mo 3C 0.52N 0.48, Co 3Mo 3C 0.62N 0.38, and Fe 3Mo 3C. We have found that they remain stable in their ambient-pressure cubic phase at least up to 48 GPa. All of them have a bulk modulus larger than 330 GPa, the least compressible material being Fe 3Mo 3C, B 0 = 374(3) GPa. In addition, apparently a reduction of compressibility is detected as the carbon content is increased. The equation of state for each material is determined. A comparison with other refractory materials indicates that interstitial nitrides and carbides behave as ultra-incompressible materials. © 2012 American Physical Society. Research supported by Spanish MCYT under Grants No. MAT2010-21270-C04-01, No. MAT2009-14144-CO3-03, and No. CSD2007-00045 (MALTA Consolider Team). XRD experiments carried out at the Diamond Light Source (I15 beamline, proposal EE6517). Errandonea, D.; Ruiz-Fuertes, J.; Sans, JA.; Santamaría-Perez, D.; Gomis Hilario, O.; Gómez, A.; Sapiña, F. (2012). Compressibility and structural stability of ultra-incompressible bimetallic interstitial carbides and nitrides. Physical Review B. 85:144103-1-144103-4. doi:10.1103/PhysRevB.85.144103 Zerr, A., Riedel, R., Sekine, T., Lowther, J. E., Ching, W. Y., & Tanaka, I. (2006). Recent Advances in New Hard High-Pressure Nitrides. Advanced Materials, 18(22), 2933-2948. doi:10.1002/adma.200501872 El-Himri, A., Sapiña, F., Ibañez, R., & Beltrán, A. (2001). Pd2Mo3N: a new molybdenum bimetallic interstitial nitride. Journal of Materials Chemistry, 11(9), 2311-2314. doi:10.1039/b101616o Errandonea, D., Ferrer-Roca, C., Martínez-Garcia, D., Segura, A., Gomis, O., Muñoz, A., … Sapiña, F. (2010). High-pressure x-ray diffraction andab initiostudy ...

Resistively heated diamond-anvil cells have been used together with synchrotron x-ray diffraction to investigate the phase diagram of calcium up to 50 GPa and 800 K. The phase boundaries between the Ca-I (fcc), Ca-II (bcc), and Ca-III (simple cubic, sc) phases have been determined at these pressure-temperature conditions, and the ambient temperature equation of state has been generated. The equation of state parameters at ambient temperature have been determined from the experimental compression curve of the observed phases by using third-order Birch-Murnaghan and Vinet equations. A thermal equation of state was also determined for Ca-I and Ca-II by combining the room-temperature Birch-Murnaghan equation of state with a Berman-type thermal expansion model. ; Part of the research was supported by the Spanish Government MINECO under Grants No. MAT2016-75586-C4-1/4P and No. MAT2015-71070-REDC. ; Peer reviewed

The structural properties of Thallium (III) oxide (Tl2O3) have been studied both experimentally and theoretically under compression at room temperature. X-ray powder diffraction measurements up to 37.7 GPa have been complemented with ab initio total-energy calculations. The equation of state of Tl2O3 has been determined and compared to related compounds. It has been found experimentally that Tl2O3 remains in its initial cubic bixbyite-type structure up to 22.0 GPa. At this pressure, the onset of amorphization is observed, being the sample fully amorphous at 25.2 GPa. The sample retains the amorphous state after pressure release. To understand the pressure-induced amorphization process, we have studied theoretically the possible high-pressure phases of Tl2O3. Although a phase transition is theoretically predicted at 5.8 GPa to the orthorhombic Rh2O3-II-type structure and at 24.2 GPa to the orthorhombic alpha-Gd2S3-type structure, neither of these phases were observed experimentally, probably due to the hindrance of the pressure-driven phase transitions at room temperature. The theoretical study of the elastic behavior of the cubic bixbyite-type structure at high-pressure shows that amorphization above 22 GPa at room temperature might be caused by the mechanical instability of the cubic bixbyite-type structure which is theoretically predicted above 23.5 GPa. (C) 2014 AIP Publishing LLC. ; This study was supported by the Spanish government MEC under Grant Nos. MAT2010-21270-C04-01/03/04, MAT2013-46649-C4-1/2/3-P, and CTQ2009-14596-C02-01, by the Comunidad de Madrid and European Social Fund (S2009/PPQ-1551 4161893), by MALTA Consolider Ingenio 2010 project (CSD2007-00045), and by Generalitat Valenciana (GVA-ACOMP-2013-1012 and GVA-ACOMP-2014-243). We acknowledge Diamond Light Source for time on beamline I15 under proposal EE6517 and I15 beamline scientist for technical support. A.M. and P.R.-H. acknowledge computing time provided by Red Espanola de Supercomputacion (RES) and MALTA-Cluster. B.G.-D. and J.A.S. ...