Search results for "COMPRESSION"
showing 10 items of 774 documents
High-pressure crystal structure, lattice vibrations, and band structure of BiSbO4
2016
The high-pressure crystal structure, lattice-vibrations HP crystal structure, lattice vibrations, and band , and electronic band structure of BiSbO4 were studied by ab initio simulations. We also performed Raman spectroscopy, infrared spectroscopy, and diffuse-reflectance measurements, as well as synchrotron powder X-ray diffraction. High-pressure X-ray diffraction measurements show that the crystal structure of BiSbO4 remains stable up to at least 70 GPa, unlike other known MTO4-type ternary oxides. These experiments also give information on the pressure dependence of the unit-cell parameters. Calculations properly describe the crystal structure of BiSbO4 and the changes induced by pressur…
Crystal structure of BaCa(CO3)2 alstonite carbonate and its phase stability upon compression
2021
Authors thank the financial support from the Spanish Ministerio de Ciencia, Innovación y Universidades (MICINN) and the Agencia Estatal de Investigación under projects MALTA Consolider Ingenio 2010 network (MAT2015-71070- REDC) and PGC2018-097520-A-I00 (cofinanced by EU FEDER funds) and from the Generalitat Valenciana under project PROMETEO/2018/123. D.S.-P. and A.O.R. acknowledge the financial support of the Spanish MINECO for RyC-2014-15643 and RyC-2016-20301 Ramón y Cajal grants, respectively. C.P. acknowledges the financial support from the Spanish Ministerio de Economia y Competitividad (MINECO project FIS2017-83295-P). Authors also thank Dr. Nicolescu and the Mineralogy and Meteoritic…
Thallium under extreme compression
2016
We present a combined theoretical and experimental study of the high-pressure behavior of thallium. X-ray diffraction experiments have been carried out at room temperature up to 125 GPa using diamond-anvil cells, nearly doubling the pressure range of previous experiments. We have confirmed the hcp-fcc transition at 3.5 GPa and determined that the fcc structure remains stable up to the highest pressure attained in the experiments. In addition, HP-HT experiments have been performed up to 8 GPa and 700 K by using a combination of x-ray diffraction and a resistively heated diamond-anvil cell. Information on the phase boundaries is obtained, as well as crystallographic information on the HT bcc …
Exploring the properties of MTO4compounds using high-pressure powder x-ray diffraction
2015
Several ternary oxides with industrial applications, but also interesting for basic research, have been studied recently at room temperature under high-pressure conditions using synchrotron powder x-ray diffraction. In this article, part of these experiments will be summarized. The studied materials include zircon-type vanadates and scheelite-type tungstates as well as other oxides related to them. Several pressure-induced structural phase transitions that take place in these compounds under compression will be here described. In addition, the determination of the crystal structure of the high-pressure phases will be discussed. The reported studies have also allowed the accurate determinati…
High-pressure/high-temperature phase diagram of zinc
2018
The phase diagram of zinc (Zn) has been explored up to 140 GPa and 6000K, by combining optical observations, x-ray diffraction, and ab initio calculations. In the pressure range covered by this study, Zn is found to retain a hexagonal close-packed (hcp) crystal symmetry up to the melting temperature. The known decrease of the axial ratio (c/a) of the hcp phase of Zn under compression is observed in x-ray diffraction experiments from 300K up to the melting temperature. The pressure at which c/a reaches root 3 (approximate to 10GPa) is slightly affected by temperature. When this axial ratio is reached, we observed that single crystals of Zn, formed at high temperature, break into multiple pol…
High-pressure structural, elastic, and thermodynamic properties of zircon-type HoPO4 and TmPO4
2017
[EN] Zircon-type holmium phosphate (HoPO4) and thulium phosphate (TmPO4) have been studied by single-crystal x-ray diffraction and ab initio calculations. We report on the influence of pressure on the crystal structure, and on the elastic and thermodynamic properties. The equation of state for both compounds is accurately determined. We have also obtained information on the polyhedral compressibility which is used to explain the anisotropic axial compressibility and the bulk compressibility. Both compounds are ductile and more resistive to volume compression than to shear deformation at all pressures. Furthermore, the elastic anisotropy is enhanced upon compression. Finally, the calculation…
ChemInform Abstract: Exploring the Properties of MTO4Compounds Using High-Pressure Powder X-Ray Diffraction
2015
Several ternary oxides with industrial applications, but also interesting for basic research, have been studied recently at room temperature under high-pressure conditions using synchrotron powder x-ray diffraction. In this article, part of these experiments will be summarized. The studied materials include zircon-type vanadates and scheelite-type tungstates as well as other oxides related to them. Several pressure-induced structural phase transitions that take place in these compounds under compression will be here described. In addition, the determination of the crystal structure of the high-pressure phases will be discussed. The reported studies have also allowed the accurate determinati…
Analytical prediction of ultimate moment and curvature of RC rectangular sections in compression
2013
This paper presents closed form expressions linking the ultimate bearing capacity to the ultimate curvature of rectangular RC sections subjected to axial load and bending moment acting in one of the two symmetry planes of the section. With respect to possible simplified formulations the following effects are also considered: confinement of the concrete, hardening of the longitudinal reinforcement, and presence of reinforcing bars distributed orthogonally to the neutral axis. The formulation is proposed in dimensional terms after a preliminary definition of the geometrical and mechanical parameters governing the structural response of the class of sections considered. The analytical expressi…
Vascular Third Nerve Compression—A Possible Cause of Episodic Vertical Diplopia?
2006
We report a 74-year-old man with a 2-year history of episodes of vertical diplopia. In the beginning, there was one episode every 2–3 months, which increased over time to an average of one episode every 2 weeks. These complaints were attributed to an MRI-documented vascular third nerve compression. Treatment with gabapentin (400 mg q.i.d.) was followed by cessation of episodic diplopia.
Spontaneous Meckel's cave hematoma: A rare cause of trigeminal neuralgia
2015
Background: The most common etiology of classic trigeminal neuralgia (TN) is vascular compression. However, other causes must be considered. Among these, spontaneous hematoma of the Meckel′s cave (MC) causing symptomatic TN is very rare. Case Description: We present the case of a 60-year-old woman with a 2-month history of left TN and diplopia. Neuroradiological examinations revealed a well-defined hematoma in the left MC. The patient underwent surgical decompression with a progressive neurological improvement. Conclusion: Despite the number of lesions potentially affecting the MC, spontaneous hemorrhage is rare but should be taken into account in the differential diagnosis.