arXiv subjects

Antoine Cornet

Publications and source records attributed to Antoine Cornet.

12 recordsLinked to original sources

arXiv2026

Multiscale Experimental Evidence of a Transitory State in the HDA-LDA Transition in Alumino-sodo-silicate Glasses

The structural evolution with temperature of pure silica (SiO2), sodium-silicate (5Na2O-95SiO2, 10Na2O-90SiO2 and 25Na2O-75SiO2) and albite (15Na2O-15Al2O3-75SiO2) glasses previously densified from hot compression is monitored with a combination of small and wide angle x-ray scattering. Transient scattering maxima in the length scales associated with both techniques indicate the presence of a transitory state, suggesting the classification of the initial and final states as distinct glass states in the context of polyamorphism. In all glasses, a transient intensity peak in the small angle scattering is observed, consistent with the nucleation of a new amorphous state. Based on a comparison with the phenomenology observed in supercooled and glassy water, we propose that this structural evolution provide a strong evidence of the glass polyamorphism as the consequence of the existence of an underlying but thermodynamically defined liquid-liquid transition, independent on the polymerization degree of the system.

cond-mat.mtrl-sci↗

arXiv2026

X-ray photo-induced atomic motion in Phase Change Materials and conventional covalent chalcogenide glasses

X-ray Photon Correlation Spectroscopy (XPCS) enables direct access to atomic-scale dynamics in disordered materials, revealing both spontaneous and X-ray-induced relaxation processes. Here, we study two compositionally similar alloy glasses near their glass transition temperatures: the phase change material (PCM) Ge15Sb85 and the non-PCM alloy Ge15Te85. Both exhibit X-ray induced atomic motion, yet with markedly different responses. Ge15Sb85 undergoes an immediate transition to a photo-induced yielding state, characterised by stationary dynamics governed solely by the absorbed dose. In contrast, Ge15Te85 shows a progressive slowing-down of the relaxation process, accompanied by a crossover from compressed to stretched exponential decay in the density autocorrelation functions. This behaviour is consistent with the emergence of liquid-like collective motion as supported by de Gennes narrowing in the wave-vector dependence of the dynamics at length scales comparable with the first sharp diffraction peak. Unlike Ge15Sb85, this alloy does not reach a stationary regime within experimental timescales, implying that the yielding transition occurs only after thousands of seconds with the available dose rate. Its response is also temperature dependent: at lower temperatures, the dynamics reflects intrinsic stress relaxation processes, whereas at higher temperatures becomes dose-controlled. These findings demonstrate that the dynamical response to X-ray excitation is not determined solely by chemical composition or bonding character, but results from the interplay between irradiation effects and structural relaxation pathways.

cond-mat.mtrl-sci↗

arXiv2025

Emergence of multiple relaxation processes during low to high density transition in Au49Cu26.9Si16.3Ag5.5Pd2.3 metallic glass

The existence of multiple amorphous states, or polyamorphism, remains one of the most debated phenomena in disordered matter, particularly regarding its microscopic origin and impact on glassy dynamics. Profiting of the enhanced data quality provided by brilliant synchrotrons, we combined high pressure X-ray photon correlation spectroscopy and X-ray diffraction to investigate the atomic dynamics-structure relationship in a Au49Cu26.9Si16.3Ag5.5Pd2.3 metallic glass at room temperature. We identify a structural and dynamical crossover near 3 GPa, marked by avalanches-like massive atomic rearrangements that promote the system toward increasingly compact atomic cluster connections. This crossover superimposes to a pressure-induced acceleration of the atomic motion recently reported, and signals the onset of a transitional state, potentially linked to the nucleation of a new phase within the glass, characterized by the coexistence of two amorphous states with distinct relaxation processes. These results provide evidence for a sluggish, continuous polyamorphic transformation, even in absence of marked structural discontinuities.

cond-mat.mtrl-sci↗

arXiv2025

Linking the pressure dependence of the structure and thermal stability to {\alpha}- and \b{eta}-relaxations in metallic glasses

Glasses derive their functional properties from complex relaxation dynamics that remain enigmatic under extreme conditions. While the temperature dependence of these relaxation processes is well-established, their behavior under high-pressure conditions remains poorly understood due to significant experimental difficulties. In this study, we employ cutting-edge experimental techniques to probe the pressure evolution of the relaxation spectrum in a Zr46.8Ti8.2Cu7.5Ni10Be27.5 metallic glass across gigapascal pressure ranges. Our findings reveal two distinct relaxation mechanisms under high pressure: In the \b{eta}-relaxation regime, compression drives the system with reduced atomic mobility and enhanced structural disorder, without significant density changes. Conversely, {\alpha}-relaxation under pressure promotes density-driven structural ordering that improves thermal stability. Notably, the transition between these regimes occurs at a constant T/Tg,P ratio, independent of applied pressure. These results provide crucial insights for decoupling the competing structural and relaxation contributions to glass stability, establishing a systematic framework for tailoring glass properties through controlled thermo-mechanical processing.

cond-mat.mtrl-sci↗

arXiv2024

Break-down of the relationship between {\alpha}-relaxation and equilibration in hydrostatically compressed metallic glasses

Glasses encode the memory of any thermo-mechanical treatment applied to them. This ability is associated to the existence of a myriad of metastable amorphous states which can be probed through different experimental pathways. It is usually assumed that this memory can be erased in the supercooled liquid, and that this process occurs on a time scale controlled by the {\alpha}-relaxation. We find that this assumption does not apply for hydrostatically compressed glasses. Annealing under pressure a prototypical metallic glass can irreversibly modify its dynamics, thermodynamics and structure, reduce the atomic mobility and lead to structural modifications of the first coordination shells which reduce the thermal stability with respect to a glass annealed in absence of pressure. When heated above their glass transition temperature, these compressed glasses do not convert into the pristine supercooled liquid, implying the existence of an additional process, beyond the {\alpha}-relaxation, contributing to the equilibrium recovery of the material. These results establish pressure as a powerful tool for engineering non-equilibrium glassy materials with tailored properties, while deepening our understanding of relaxation dynamics in disordered systems under extreme conditions.

cond-mat.mtrl-sci↗

arXiv2024

On the interplay of liquid-like and stress-driven dynamics in a metallic glass former observed by temperature scanning XPCS

Modern detector technology and highly brilliant fourth-generation synchrotrons allow to improve the temporal resolution in time-resolved diffraction studies. Profiting from this, we applied temperature scanning X-ray photon correlation spectroscopy (XPCS) to probe the dynamics of a Pt-based metallic glass former in the glass, glass transition region, and supercooled liquid, covering up to six orders of magnitude in time scales. Our data demonstrates that the structural alpha-relaxation process is still observable in the glass, although it is partially masked by a faster source of decorrelation observed at atomic scale. We present an approach that interprets these findings as the superposition of heterogeneous liquid-like and stress-driven ballistic-like atomic motions. This work not only extends the dynamical range probed by standard isothermal XPCS, but also clarifies the fate of the alpha-relaxation across the glass transition and provides a new perception on the anomalous, compressed temporal decay of the density-density correlation functions observed in metallic glasses and many out-of-equilibrium soft materials.

cond-mat.mtrl-sci↗

arXiv2024

High-pressure X-ray photon correlation spectroscopy at fourth-generation synchrotron sources

A new experimental setup combining X-Ray Photon Correlation Spectroscopy (XPCS) in the hard x-ray regime and a high-pressure sample environment is developed to monitor the pressure dependence of the internal motion of complex systems down to the atomic scale in the multi-gigapascal range, from room temperature to 600K. The high flux of coherent high energy x-rays at 4th generation synchrotron source solves the problems caused by the absorption of the Diamond Anvil Cells used to generate the high pressure, enabling the measurement of the intermediate scattering function over 6 orders of magnitude in time, from $10^{-3}$ s to $10^{3}$s. The constraints posed by the high-pressure generation such as the preservation of X-ray coherence, as well as the sample, pressure and temperature stability, are discussed, and the feasibility of high-pressure XPCS is demonstrated through results obtained on metallic glasses.

physics.app-ph↗

arXiv2024

Structural modifications of GeO$_2$ glass under high pressure and high temperature

Vitreous GeO$_2$ has been compressed at high temperature, to investigate the effect of thermal activation on the structural reorganization during compression. The measurements were performed in-situ using micro Raman spectroscopy under pressure up to 6 GPa and temperature up to 400$^\circ$C. The evolution of the Raman shift of the main band (400-500 cm$^{-1}$) with temperature during compression evidences a pressure window around 3 GPa within which temperature has a remarkable influence on the structure, in particular the intermediate range order. We find that this change is well correlated with previous ex-situ density measurements from high pressure-high temperature densifications. Moreover, coordination changes from tetrahedrally (GeO$_4$) to octahedrally (GeO$_6$) coordinated GeO$_2$ are accelerated with the heating during the compression.

physics.app-ph↗

arXiv2024

Relaxation processes of densified silica glass

Densified SiO2 glasses, obtained from different pressure and temperature routes have been annealed over a wide range of temperature far below the glass transition temperature (500$^\circ$C-900$^\circ$C). Hot and cold compressions were useful to separate the effects of pressure and the compression temperature. In-situ micro-Raman spectroscopy was used to follow the structural evolution during the thermal relaxation. A similar glass structure between the non-densified silica and the recovered densified silica after the temperature annealing demonstrates a perfect recovery of the non-densified silica glass structure. While the density decreases monotonically, the structural relaxation takes place through a more complex mechanism, which shows that density is not a sufficient parameter to fully characterize the structure of densified silica glass. The relaxation takes place through a transitory state, consisting in an increase of the network inhomogeneity, shown by an increase in intensity of the D2 band which is associated with 3 membered rings. The activation energy of these processes is 255$\pm$45 kJ/mol for the hot compressed samples. The kinetic is overall faster for the cold compressed samples. In that last case the relaxation is partially activated by internal stresses release.

physics.chem-ph↗

arXiv2024

Evidence of polyamorphic transitions during densified SiO$_2$ glass annealing

In-situ X-ray scattering monitoring is carried out during temperature annealing on different densified SiO$_2$ glasses. Density fluctuations and intermediate range coherence from x-ray scattering (SAXS) and diffraction (WAXS) evidence a maximum in their evolution at the same relaxation time. These extrema confirm the existence of an intermediate transitory disordered state between the two more ordered high and low density amorphous states. We propose that the existence of this transitory state confirms the existence of two mega basin in the energy landscape and therefore an amorphous-amorphous transition. Including older Raman results, we show that this intermediate disorder state implies similar mechanisms at all length scales from a few angstroms to 5 nm.

physics.chem-ph↗

arXiv2024

Permanently densified SiO$_2$ glasses: a structural approach

Densified silica can be obtained by different pressure and temperature paths and for different stress conditions, hydrostatic or including shear. The density is usually the macroscopic parameter used to characterize the different compressed silica samples. The aim of our present study is to compare structural modifications for silica glass, densified from several routes. For this, densified silica glasses are prepared from cold and high temperature (up to 1020 $^\circ$C) compressions. The different densified glasses obtained in our study are characterized by micro-Raman spectroscopy. Intertetrahedral angles from the main band relative to the bending mode decreases and their values are larger for densified samples from high temperature compression than those samples from cold compression. The relative amount of 3-membered rings deduced from the D2 line area increases as a function of density for cold compression. The temperature increase during the compression process induces a decrease of the 3 fold ring population. Moreover, 3 fold rings are more deformed and stressed for densified samples at room temperature at the expense of those densified at high temperature. Temperature plays a main role in the reorganization structure during the densification and leads to obtaining a more relaxed structure with lower stresses than glasses densified from cold compression. The role of hydrostatic or non-hydrostatic applied stresses on the glass structure is discussed. From the Sen and Thorpe central force model, intertetrahedral angle average value and their distribution are estimated.

cond-mat.mtrl-sci↗

arXiv2023

Directly observing atomic-scale relaxations of a glass forming liquid using femtosecond X-ray photon correlation spectroscopy

Glass forming liquids exhibit structural relaxation behaviors, reflecting underlying atomic rearrangements on a wide range of timescales. These behaviors play a crucial role in determining many material properties. However, the relaxation processes on the atomic scale are not well understood due to the experimental difficulties in directly characterizing the evolving correlations of atomic order in disordered systems. Here, taking the model system Ge15Te85, we demonstrate an experimental approach that probes the relaxation dynamics by scattering the coherent X-ray pulses with femtosecond duration produced by X-ray free electron lasers (XFELs). By collecting the summed speckle patterns from two rapidly successive, nearly identical X-ray pulses generated using a split-delay system, we can extract the contrast decay of speckle patterns originating from sample dynamics and observe the full decorrelation of local order on the sub-picosecond timescale. This provides the direct atomic-level evidence of fragile liquid behavior of Ge15Te85. Our results demonstrate the strategy for XFEL-based X-ray photon correlation spectroscopy (XPCS), attaining femtosecond temporal and atomic-scale spatial resolutions. This twelve orders of magnitude extension from the millisecond regime of synchrotron-based XPCS opens a new avenue of experimental studies of relaxation dynamics in liquids, glasses, and other highly disordered systems.

cond-mat.mtrl-sci↗