High-pressure study of X-ray diffuse scattering in ferroelectric perovskites

We present a high-pressure x-ray diffuse scattering study of the ABO$_3$ ferroelectric perovskites BaTiO_3 and KNbO_3. The well-known diffuse lines are observed in all the phases studied. In KNbO_3, we show that the lines are present up to 21.8 GPa, with constant width and a slightly decreasing intensity. At variance, the intensity of the diffuse lines observed in the cubic phase of BaTiO_3 linearly decreases to zero at $\sim 11$ GPa. These results are discussed with respect to x-ray absorption measurements, which leads to the conclusion that the diffuse lines are only observed when the B atom is off the center of the oxygen tetrahedron. The role of such disorder on the ferroelectric instability of perovskites is discussed.Comment: 4 pages, Accepted in PR

Corporate reputation past and future: a review and integration of existing literature and a framework for future research

The concept of corporate reputation is steadily growing in interest among management researchers and practitioners. In this article, we trace key milestones in the development of reputation literature over the past six decades to suggest important research gaps as well as to provide contextual background for a subsequent integration of approaches and future outlook. In particular we explore the need for better categorised outcomes; a wider range of causes; and a deeper understanding of contingencies and moderators to advance the field beyond its current state while also taking account of developments in the macro business environment. The article concludes by presenting a novel reputation framework that integrates insights from reputation theory and studies, outlines gaps in knowledge and offers directions for future research

Pressure dependence of expansivity in the liquid hexane as a model for liquids

Along isothermal paths, the expansivity of liquid hexane is shown to follow a power law up to a few hundred MPa. The pole of this function is found to be close to the expected limits of thermodynamic stability (spinodal) of the liquid state. Analysis of argon and carbon dioxide data shows that the model may be extended to other liquids. A similar equation may be used to fit the isothermal compressibility data.A température constante, le coefficient de dilatation de l'hexane liquide obéit à une fonction en puissance de la pression jusqu'à plusieurs centaines de MPa. On observe que le pôle de cette fonction est situé à proximité du lieu estimé de la spinodale de l'état liquide. L'examen des données montre que cette propriété s'étend à d'autres liquides. Une forme similaire peut être utilisée pour décrire la variation de la compressibilité isotherme avec la pression

Internal raman spectrum of ammonia up to 75 GPa suggesting the loss of the molecular character above about 60 GPa

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Partial order in ice VII determined by raman spectroscopy

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Polymerization of benzene and thiophene at high pressure: What is the reaction path?

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Raman Spectroscopy Investigation of Ice VII and Deuterated Ice VII to 40 GPa. Disorder in Ice VII

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Pressure effects on the Raman spectra of 3-deutero-ammonia, lattica dynamics and vibrons up to 40 GPa

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Raman scattering study of ammonia up to 75 GPa: Evidence for bond symmetrization at 60 GPa

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Vibrational dynamics and phase diagram of KNbO3 up to 30G Pa and from 20 to 500K

International audienceD ow n lo a de d B y : [B IU S J u s s ie The phase diagramof KNbO3 was investigatedby Ramanscattering upto 30GPaandfrom10to500K(750Kat 2GPa). Macroscopic ferroelectricity vanishes on compressionand the various ferroelectric solids, rhombohedral, orthorhombicandtetragonal (R–O–T), werefoundtoexist inclosedomainsof thepressure–temperatureplane.SpecificallytheTsolidvanishesbelow200Kand theRandOsolidsexist, verylikely, downto0K. Quantumsuppressionof the Rsolidlikelyoccursbelow100K.Thetransitiontothecubicparaelectricphaseis ofthedisplacivetypeatlowtemperaturewhereasitisoftheorder–disordertype athightemperature. Inthecubicsolid, first-orderRamanscattering, assignedto structural distortionduetodynamical disorder, wasobserved. Thedistortionis orthorhombicbelow200Kandtetragonalabove,whichmaystemfromtherapid decreasewithtemperatureof theNbiondwellingtimeinitsallowedsites