Low-frequency Raman scattering under high pressure in diamond anvil cell: Experimental protocol and application to GeO2 and SiO2 boson peaks

Deschamps, Thierry; Martinet, C.; Ligny, Dominique de; Bruneel, Jean‐Luc; Champagnon, B.

doi:10.1016/j.jnoncrysol.2012.08.021

Cited by 14 publications

(10 citation statements)

References 52 publications

(68 reference statements)

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“…Thus, the longitudinal sound velocity exhibits a minimum as a function of the densification ratio. Such behaviour recalls the well-known compressibility anomaly observed in silica glass under pressure, between P atmo and 3 GPa 39 40 41 42 43 44 45 46 47 48 . Nevertheless, these two anomalies need to be clearly distinguished: one appears after plastic deformation while the other takes place in the elastic regime of silica glass.…”

Section: Resultssupporting

confidence: 85%

“…Between P atmo and 3 GPa, reversible structural transitions similar to those which underlie the β→α transition in cristobalite, first suggested by Vukcevich 36 , were recently observed in molecular-dynamic simulations 44 45 . This change in the six-fold ring conformation is responsible for the softening of the elastic moduli under pressure, i.e the well-known “compressibility anomaly” 39 40 41 42 43 . Indeed, the β-like rings, which are more symmetric than α-like rings, have higher elastic moduli.…”

Section: Discussionmentioning

confidence: 99%

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Elastic Moduli of Permanently Densified Silica Glasses

Deschamps

Margueritat

Martinet

et al. 2014

Sci Rep

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Modelling the mechanical response of silica glass is still challenging, due to the lack of knowledge concerning the elastic properties of intermediate states of densification. An extensive Brillouin Light Scattering study on permanently densified silica glasses after cold compression in diamond anvil cell has been carried out, in order to deduce the elastic properties of such glasses and to provide new insights concerning the densification process. From sound velocity measurements, we derive phenomenological laws linking the elastic moduli of silica glass as a function of its densification ratio. The found elastic moduli are in excellent agreement with the sparse data extracted from literature, and we show that they do not depend on the thermodynamic path taken during densification (room temperature or heating). We also demonstrate that the longitudinal sound velocity exhibits an anomalous behavior, displaying a minimum for a densification ratio of 5%, and highlight the fact that this anomaly has to be distinguished from the compressibility anomaly of a-SiO2 in the elastic domain.

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Section: Resultssupporting

confidence: 85%

Section: Discussionmentioning

confidence: 99%

Elastic Moduli of Permanently Densified Silica Glasses

Deschamps

Margueritat

Martinet

et al. 2014

Sci Rep

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“…In all three considerations, the Boson peak is directly or indirectly related to structural heterogeneity of the solid glass, typically on the scale of a few nanometers. It has further been shown extensively that its frequency (ω BP ) and intensity ( I BP ) depend not only on glass composition, but also on thermal history, pressure and the presence of different polymorphic states . Regarding the pressure‐dependence, analyses have been carried‐out primarily in quasi‐isostatic conditions, in situ using diamond anvil cells or ex situ through high temperature/high pressure multianvil set‐ups …”

Section: Introductionmentioning

confidence: 99%

Local Deformation of Glasses is Mediated by Rigidity Fluctuation on Nanometer Scale

et al. 2018

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Microscopic deformation processes determine defect formation on glass surfaces and, thus, the material's resistance to mechanical failure. While the macroscopic strength of most glasses is not directly dependent on material composition, local deformation and flaw initiation are strongly affected by chemistry and atomic arrangement. Aside from empirical insight, however, the structural origin of the fundamental deformation modes remains largely unknown. Experimental methods that probe parameters on short or intermediate length‐scale such as atom–atom or superstructural correlations are typically applied in the absence of alternatives. Drawing on recent experimental advances, spatially resolved Raman spectroscopy is now used in the THz‐gap for mapping local changes in the low‐frequency vibrational density of states. From direct observation of deformation‐induced variations on the characteristic length‐scale of molecular heterogeneity, it is revealed that rigidity fluctuation mediates the deformation process of inorganic glasses. Molecular field approximations, which are based solely on the observation of short‐range (interatomic) interactions, fail in the prediction of mechanical behavior. Instead, glasses appear to respond to local mechanical contact in a way that is similar to that of granular media with high intergranular cohesion.

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“…Double or triple monochromators are typically used to record the LF Raman range [30,65,66]. Recently, ultranarrow band laser rejection filters have become available that allow measurements at < 10 cm -1 [67].…”

Section: Low-frequency Raman Spectroscopymentioning

confidence: 99%

Application of Vibrational Spectroscopy to Study Solid-state Transformations of Pharmaceuticals

Erxleben

2016

CPD

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Understanding the properties, stability and transformations of the solid-state forms of an active pharmaceutical ingredient (API) in the development pipeline is of crucial importance for process-development, formulation development and FDA approval. Investigation of the polymorphism and polymorphic stability is a routine part of the preformulation studies. Vibrational spectroscopy allows the real-time in situ monitoring of phase transformations and probes intermolecular interactions between API molecules, between API and polymer in amorphous solid dispersions or between API and coformer in cocrystals or coamorphous systems and thus plays a major role in efforts to gain a predictive understanding of the relative stability of solid-state forms and formulations. Infrared (IR), near-infrared (NIR) and Raman spectroscopies, alone or in combination with other analytical methods, are important tools for studying transformations between different crystalline forms, between the crystalline and amorphous form, between hydrate and anhydrous form and for investigating solid-state cocrystal formation. The development of simple-to-use and cost-effective instruments on the one hand and recent technological advances such as access to the low-frequency Raman range down to 5 cm-1, on the other, have led to an exponential growth of the literature in the field. This review discusses the application of IR, NIR and Raman spectroscopies in the study of solid-state transformations with a focus on the literature published over the last eight years.

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Low-frequency Raman scattering under high pressure in diamond anvil cell: Experimental protocol and application to GeO2 and SiO2 boson peaks

Cited by 14 publications

References 52 publications

Elastic Moduli of Permanently Densified Silica Glasses

Elastic Moduli of Permanently Densified Silica Glasses

Local Deformation of Glasses is Mediated by Rigidity Fluctuation on Nanometer Scale

Application of Vibrational Spectroscopy to Study Solid-state Transformations of Pharmaceuticals

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