High-resolution inelastic x-ray scattering to study the high-frequency atomic dynamics of disordered systems

Monaco, G.

doi:10.1016/j.crhy.2007.10.017

Cited by 7 publications

(4 citation statements)

References 61 publications

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“…Within the context of large literature about intermolecular vibrational dynamics of glass-forming liquids, the band at ∼20 cm –1 seen in low-frequency Raman spectra of the glassy phase of ionic liquids (see Figure ) is the so-called boson peak. − ,− ,,− It has been pointed out that the boson peak vibrations remain in the liquid state even though the peak is hidden under the intense quasi-elastic scattering of the low-frequency Raman spectrum. − In an OKE spectroscopy study of 1-ethyl-3-methylimidazolium tosylate, Li et al assigned to the boson peak dynamics the oscillatory component with period of ∼2.0 ps (i.e., ∼17 cm –1 ) seen in the time domain data a few degrees above the glass transition temperature ( T g = 201 K). The partial nature of longitudinal and transverse acoustic modes of the intermolecular dynamics in the spatial range of wavevectors 0.1 < k < 1.0 Å –1 and frequency range 0 < ω < 100 cm –1 in viscous glass-forming liquids has been established in many studies by inelastic X-ray scattering spectroscopy and MD simulations. − Although the exact origin of the boson peak is yet a lively debated issue, several studies have been pointing to the nature of transverse acoustic vibrations of high wave-vectors (i.e., soundlike modes of short wavelength). − It is worth stressing that projecting into soundlike modes recovers only part of the intermolecular vibrations of liquids because the other part is random phase motion ,,, and eventually molecular-like normal modes in high temperature molten salts in which complexes survive for a relatively long time. , …”

Section: Vibrational Spectroscopy Of Pure Ionic Liquids In the Low-fr...mentioning

confidence: 99%

Vibrational Spectroscopy of Ionic Liquids

2017

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Vibrational spectroscopy has continued use as a powerful tool to characterize ionic liquids since the literature on room temperature molten salts experienced the rapid increase in number of publications in the 1990's. In the past years, infrared (IR) and Raman spectroscopies have provided insights on ionic interactions and the resulting liquid structure in ionic liquids. A large body of information is now available concerning vibrational spectra of ionic liquids made of many different combinations of anions and cations, but reviews on this literature are scarce. This review is an attempt at filling this gap. Some basic care needed while recording IR or Raman spectra of ionic liquids is explained. We have reviewed the conceptual basis of theoretical frameworks which have been used to interpret vibrational spectra of ionic liquids, helping the reader to distinguish the scope of application of different methods of calculation. Vibrational frequencies observed in IR and Raman spectra of ionic liquids based on different anions and cations are discussed and eventual disagreements between different sources are critically reviewed. The aim is that the reader can use this information while assigning vibrational spectra of an ionic liquid containing another particular combination of anions and cations. Different applications of IR and Raman spectroscopies are given for both pure ionic liquids and solutions. Further issues addressed in this review are the intermolecular vibrations that are more directly probed by the low-frequency range of IR and Raman spectra and the applications of vibrational spectroscopy in studying phase transitions of ionic liquids.

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Section: Vibrational Spectroscopy Of Pure Ionic Liquids In the Low-fr...mentioning

confidence: 99%

Vibrational Spectroscopy of Ionic Liquids

2017

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“…Momentum-resolved Inelastic X-ray Scattering (IXS) with meV energy resolution provides a powerful technique for studying vibrational dynamics and excitations in condensed matter systems [1]. The scientific objective of the IXS beamline of NSLS-II is focused on very high-resolution (1 meV ~ 0.1 meV) IXS experiments.…”

Section: Introductionmentioning

confidence: 99%

“…With the 0.1 meV energy resolution, we anticipate improved understanding of the low-energy excitations in liquid, disordered and bio-molecular systems, where atomic motions due to the naturally occurring inhomogeneity and/or density fluctuations dominate the scattering at low momentum transfer (Q), for which very high Q resolution (< 0.1 nm -1 ) would also be required. Achieving these goals would allow the NSLS-II IXS beamline to bridge, at least partially, the dynamic gap (0.1 nm -1 < Q < 2 nm -1 and 0.1 meV < E < 5 meV) between various existing inelastic scattering probes [1]. This is an area where potential new science may be expected.…”

Section: Introductionmentioning

confidence: 99%

The Ultrahigh Resolution IXS Beamline of NSLS-II: Recent Advances and Scientific Opportunities

Cai

Coburn

Cunsolo

et al. 2013

J. Phys.: Conf. Ser.

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The ultrahigh resolution IXS beamline of NSLS-II is designed to probe a region of dynamic response that requires an ultrahigh energy and momentum resolution of up to 0.1 meV and < 0.1 nm-1 , respectively, which is currently still beyond the reach of existing low and high frequency inelastic scattering probes. Recent advances at NSLS-II in developing the required x-ray optics and instrumentation based on the use of extremely asymmetric Bragg back reflections of Si have allowed us to achieve sub-meV energy resolution with sharp tails and high efficiency at a medium energy of around 9.1 keV, thereby validating the optical design of the beamline for the baseline scope and paving the way for further development towards the ultimate goal of 0.1 meV. The IXS beamline is expected to provide a broad range of scientific opportunities, particularly in areas of liquid, disordered and bio-molecular systems.

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“…Similarly to what happens in single crystals, at a given pressure, the dependence of the acoustic excitation energy on momentum transfer can be plotted in a diagram and follows a dispersing curve, the so-called longitudinal acoustic dispersion relation for the amorphous material. The dispersion relation has an almost linear dependence on Q when Q tends to zero and its slope at this limit corresponds to the macroscopic longitudinal sound velocity [39]. The dispersion curves behave like a typical sinusoidal function that peaks at momentum transfers between 10 and 12 nm −1 , depending on the applied pressure.…”

Section: Mechanical Propertiesmentioning

confidence: 94%

Characterization of the structure, stability, mechanical and electrochemical properties of metallic glasses

Duarte Correa

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Metallic glasses are often referred as glassy or amorphous alloys. They lack long-range order and microstructural defects that are characteristics in crystals, such as grain and phase boundaries and dislocations. These new materials have demonstrated very interesting structural and mechanical properties derived from their homogeneity in composition and the absence of grain boundaries. Structural, mechanical or chemical properties, among others, may be even superior to those observed in conventional metallic alloys, and therefore attracted great scientific and technological interest. In this thesis project three different families of metallic glasses were selected to achieve a better understanding of amorphous alloys. First, a Ce-based alloy has been used to analyze a polyamorphic transition upon application of pressure to a more densely packed structure. X-ray diffraction and inelastic x-ray scattering data show a polyamorphic transition in the 2-10 GPa range, and this transition presents a hysteresis cycle between both compression and decompression data. The effect of this transition on mechanical properties is then evaluated. Second, a family of Fe-based metallic glasses, or amorphous steels, was selected to study their mechanical and electrochemical properties as a function of the structure and composition. The composition of the base alloy was first modified by addition of Yttrium in different concentrations as microalloying element and the structure was changed by thermal annealing, forming intermediate crystal/amorphous composites, up to a complete crystallization state. Finally, an entirely new alloy for biocompatible purposes has been designed, synthesized, and characterized. The basic structural characterization of this new Zr-Ti based amorphous alloy shows that is possible to produce the amorphous state in an alloy that does not contain toxic or unhealthy elements. Los vidrios metálicos, comúnmente conocidos como aleaciones amorfas o vitrificadas, carecen de orden a largo alcance así como de defectos microestructurales comunes en los cristales, tales como dislocaciones o fronteras de grano y/o de fase. Esta nueva clase de materiales ha demostrado poseer propiedades muy interesantes derivadas de la ausencia de microestructura y la homogeneidad en su composición. Estas propiedades, estructurales, mecánicas y químicas, entre otras, pueden llegar a ser incluso superiores a las observadas en materiales convencionales, y por lo tanto los vidrios metálicos han atraído gran interés por parte de la comunidad científica así como de carácter tecnológico. En este proyecto de tesis se pretende obtener un mayor conocimiento sobre aleaciones metálicas amorfas, para lo cual se propusieron tres familias diferentes de vidrios metálicos. Primero, se utilizó una aleación de base Ce para analizar transiciones poliamórficas, entre un estado de baja densidad hacia una estructura densamente empaquetada, por efecto de la presión. Los resultados obtenidos por difracción de rayos X y dispersión inelástica de rayos X muestran una transición en un rango de presiones de 2 a 10 GPa presentando además histéresis con respecto a los datos obtenidos en compresión y descompresión. El efecto de dicha transición en las propiedades mecánicas de la aleación es también evaluado. En segundo lugar se eligió una familia de aleaciones de base Fe, conocidos también como aceros amorfos. Las propiedades mecánicas y electroquímicas en función de la estructura y la composición fueron evaluadas mediante la introducción de itrio como elemento microaleante y la modificación de la estructura por medio de tratamientos térmicos con la obtención de estructuras compuestas nanocristal-amorfo hasta una completa cristalización. Finalmente, se diseñó y sintetizó una aleación completamente nueva con el propósito de evaluar biocompatibilidad. La caracterización estructural básica de esta nueva aleación de base Zr-Ti sin elementos tóxicos y/o alergénicos muestra que es posible obtener aleaciones amorfas con las composiciones propuestas

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High-resolution inelastic x-ray scattering to study the high-frequency atomic dynamics of disordered systems

Cited by 7 publications

References 61 publications

Vibrational Spectroscopy of Ionic Liquids

Vibrational Spectroscopy of Ionic Liquids

The Ultrahigh Resolution IXS Beamline of NSLS-II: Recent Advances and Scientific Opportunities

Characterization of the structure, stability, mechanical and electrochemical properties of metallic glasses

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