Showing 1–9 of 9 results for author: Bove, L E

Negative Thermal Expansion in Cubic Ice: A Collective Quantum Effect of the hydrogen-bond network

Authors: Loan Renaud, Tomasz Poreba, Richard Gaal, A. Marco Saitta, Michele Casula, Livia Eleonora Bove

Abstract: We report neutron powder diffraction measurements and path-integral molecular dynamics simulations of stacking-disorder-free cubic ice I$_c$, produced by topotactic degassing of C2 hydrogen hydrate. Across the cryogenic stability range, ice I$_c$ exhibits a density maximum near 70 K, closely matching that of hexagonal ice I$_h$ despite their different long-range stacking sequences. Negative therma… ▽ More We report neutron powder diffraction measurements and path-integral molecular dynamics simulations of stacking-disorder-free cubic ice I$_c$, produced by topotactic degassing of C2 hydrogen hydrate. Across the cryogenic stability range, ice I$_c$ exhibits a density maximum near 70 K, closely matching that of hexagonal ice I$_h$ despite their different long-range stacking sequences. Negative thermal expansion in ice I is therefore not specific to hexagonal stacking, but arises from the shared open tetrahedral hydrogen-bond network. Simulations with the MB-pol potential quantitatively reproduce the experimental anomaly only when nuclear quantum effects are included. The density maximum coincides, within the temperature resolution, with maximal anisotropy of the proton quantum distribution. Neutron-derived displacement parameters independently reveal a strongly enhanced transverse proton displacement, while phonon calculations identify low-frequency transverse modes with the most negative Grüneisen parameters. Together, these results establish the negative thermal expansion of ice I as a collective quantum effect governed by nuclear statistics and the dynamics of the hydrogen-bond network. △ Less

Submitted 30 July, 2026; originally announced July 2026.

Cryogenic stabilization of molecular hydrogen in dense cubic ice

Authors: Tomasz Poręba, Leon Andriambariarijaona, Richard Gaal, Kazuki Komatsu, Gaston Garbarino, Thomas Hansen, Stanislav Savvin, Livia E. Bove

Abstract: Hydrogen is widely regarded as a cornerstone of future low-carbon energy technologies, yet the lack of safe, efficient, and reversible solid-state storage materials remains a major barrier to its large-scale deployment. Although porous frameworks and metal hydrides have been extensively explored, far less is known about the ability of dense molecular solids to stabilize hydrogen at near-ambient pr… ▽ More Hydrogen is widely regarded as a cornerstone of future low-carbon energy technologies, yet the lack of safe, efficient, and reversible solid-state storage materials remains a major barrier to its large-scale deployment. Although porous frameworks and metal hydrides have been extensively explored, far less is known about the ability of dense molecular solids to stabilize hydrogen at near-ambient pressure. Here we show that fully crystalline cubic ice, despite its non-porous nature, can retain molecular hydrogen as an interstitial guest following controlled decompression from a high-pressure hydrogen hydrate precursor. Using synchrotron X-ray diffraction, neutron diffraction, and Raman spectroscopy, we demonstrate that hydrogen is retained within the ice structure up to about 130 K, producing reproducible lattice expansion and distinct spectroscopic signatures. We further show that pure cubic ice can be partially refilled with hydrogen at 0.18 GPa and 130 K, while fully hydrogen-filled cubic structure can be preserved at the same pressure up to 90 K. The retained hydrogen content reaches several percent of the parent hydrate composition, corresponding to gravimetric and volumetric storage densities comparable to those of interstitial hydrogen in metals. These results reveal an unexpected ability of a dense hydrogen-bonded crystal structure to host molecular hydrogen without permanent porosity or chemical bonding, establishing cubic ice as a minimal model for hydrogen-lattice interactions. More broadly, our findings identify dense hydrogen-bonded solids as an unexplored class of materials for hydrogen storage physics, with implications extending from energy materials to planetary and astrophysical ice environments. △ Less

Submitted 1 April, 2026; originally announced April 2026.

Dual quantum locking: Dynamic coupling of hydrogen and water sublattices in hydrogen filled ice

Authors: Loan Renaud, Tomasz Poreba, Simone Di Cataldo, Alasdair Nicholls, Léon Andriambariarijaona, Maria Rescigno, Richard Gaal, Michele Casula, A. Marco Saitta, Livia Eleonora Bove

Abstract: Hydrogen hydrates (HH) are a unique class of materials composed of hydrogen molecules confined within crystalline water frameworks. Among their multiple phases, the filled ice structures, particularly the cubic C2 phase, exhibit exceptionally strong host-guest interactions due to ultra-short H2-H2O distances and a 1:1 stoichiometry leading to two interpenetrated identical diamond-like sublattices,… ▽ More Hydrogen hydrates (HH) are a unique class of materials composed of hydrogen molecules confined within crystalline water frameworks. Among their multiple phases, the filled ice structures, particularly the cubic C2 phase, exhibit exceptionally strong host-guest interactions due to ultra-short H2-H2O distances and a 1:1 stoichiometry leading to two interpenetrated identical diamond-like sublattices, one comprised of water molecules, the other of hydrogen molecules. At high pressures, nuclear quantum effects involving both hydrogen molecules and the water lattice become dominant, giving rise to a dual-lattice quantum system. In this work, we explore the sequence of pressure- and temperature-driven phase transitions in HH, focusing on the interplay between molecular rotation, orientational ordering, lattice symmetry breaking and hydrogen bond symmetrization. Using a combination of computational modeling based on classical and path-integral molecular dynamics, quantum embedding, and high pressure experiments, including Raman spectroscopy and synchrotron X-ray diffraction at low temperatures and high pressures, we identify signatures of quantum-induced ordering and structural transformations in the C2 phase. Our findings reveal that orientational ordering in HH occurs at much lower pressures than in solid hydrogen, by inducing structural changes in the water network and enhancing the coupling of water and hydrogen dynamics. This work provides new insights into the quantum behavior of hydrogen under extreme mechanochemical confinement and establishes hydrogen-filled ices as a promising platform for the design of hydrogen-rich quantum materials. △ Less

Submitted 29 October, 2025; originally announced October 2025.

Discovery of a low-density filled-ice phase in nitrogen hydrate at high pressure

Authors: Selene Berni, Sophie Espert, Tomasz Poreba, Simone Di Cataldo, Richard Gaal, Gabriel Tobie, Erwan Le Menn, Thomas C. Hansen, Roberto Bini, Livia Eleonora Bove

Abstract: We map the high-pressure phase diagram of nitrogen hydrate up to 16 GPa at room temperature by combining neutron diffraction, Raman spectroscopy, and crystal structure prediction. We reveal a rich sequence of structural transformations, from sI/sII clathrates to hexagonal (sH) and tetragonal (sT) phases, culminating in a previously unknown orthorhombic filled-ice structure above 1.8 GPa in the Pnm… ▽ More We map the high-pressure phase diagram of nitrogen hydrate up to 16 GPa at room temperature by combining neutron diffraction, Raman spectroscopy, and crystal structure prediction. We reveal a rich sequence of structural transformations, from sI/sII clathrates to hexagonal (sH) and tetragonal (sT) phases, culminating in a previously unknown orthorhombic filled-ice structure above 1.8 GPa in the Pnma space group, which we designate as NH-V. This new phase cannot be indexed to any known ice frameworks - such as the high-pressure methane hydrates MH-III (Imma) or MH-IV (Pmcn) - and exhibits a density approximately 30% lower than that of stable ice VII, pointing to distinctive water-nitrogen interactions. Our results refine the understanding of nitrogen hydrate behavior under extreme conditions and demonstrate the propensity of nitrogen and water to form stable filled-ice structures up to 16 GPa, with important implications for planetary science. △ Less

Submitted 13 August, 2025; originally announced August 2025.

Hydrogen bond symmetrization in high-pressure ice clathrates

Authors: Lorenzo Monacelli, Maria Rescigno, Alasdair Nicholls, Umbertoluca Ranieri, Simone Di Cataldo, Livia Eleonora Bove

Abstract: Hydrogen bond symmetrization is a fundamental pressure-induced transformation in which the distinction between donor and acceptor sites vanishes, resulting in a symmetric hydrogen-bond network. While extensively studied in pure ice, most notably during the ice VII to ice X transition, this phenomenon remains less well characterized in hydrogen hydrates. In this work, we investigate hydrogen bond s… ▽ More Hydrogen bond symmetrization is a fundamental pressure-induced transformation in which the distinction between donor and acceptor sites vanishes, resulting in a symmetric hydrogen-bond network. While extensively studied in pure ice, most notably during the ice VII to ice X transition, this phenomenon remains less well characterized in hydrogen hydrates. In this work, we investigate hydrogen bond symmetrization in the high-pressure phases of hydrogen hydrate (H2-H2O and H2-D2O) through a combined approach of Raman spectroscopy and first-principles quantum atomistic simulations. We focus on the C2 and C3 filled-ice phases, using both hydrogenated and deuterated water frameworks. Our results reveal that quantum fluctuations and the interaction between the encaged H2 molecules and the host lattice play a crucial role in driving the symmetrization process. Remarkably, we find that in both C2 and C3 phases, hydrogen bond symmetrization occurs via a continuous crossover at significantly lower pressures than in pure ice, without any change in the overall crystal symmetry. These findings provide new insight into the quantum-driven mechanisms of bond symmetrization in complex hydrogen-bonded systems under extreme conditions. △ Less

Submitted 16 June, 2025; originally announced June 2025.

Comments: 8 pages, 6 figures

Giant splitting of the hydrogen rotational eigenenergies in the C$_2$ filled ice

Authors: Simone Di Cataldo, Maria Rescigno, Lorenzo Monacelli, Umbertoluca Ranieri, Richard Gaal, Stefan Klotz, Jacques Ollivier, Michael Marek Koza, Cristiano De Michele, Livia Eleonora Bove

Abstract: Hydrogen hydrates present a rich phase diagram influenced by both pressure and temperature, with the so-called C$_2$ phase emerging prominently above 2.5 GPa. In this phase, hydrogen molecules are densely packed within a cubic ice-like lattice and the interaction with the surrounding water molecules profoundly affects their quantum rotational dynamics. Herein, we delve into this intricate interpla… ▽ More Hydrogen hydrates present a rich phase diagram influenced by both pressure and temperature, with the so-called C$_2$ phase emerging prominently above 2.5 GPa. In this phase, hydrogen molecules are densely packed within a cubic ice-like lattice and the interaction with the surrounding water molecules profoundly affects their quantum rotational dynamics. Herein, we delve into this intricate interplay by directly solving the Schrödinger's equation for a quantum H$_2$ rotor in the C$_2$ crystal field at finite temperature, generated through Density Functional Theory. Our calculations reveal a giant energy splitting relative to the magnetic quantum number of $\pm$3.2 meV for $l=1$. Employing inelastic neutron scattering, we experimentally measure the energy levels of H$_2$ within the C$_2$ phase at 6.0 and 3.4 GPa and low temperatures, finding remarkable agreement with our theoretical predictions. These findings underscore the pivotal role of hydrogen--water interactions in dictating the rotational behavior of the hydrogen molecules within the C$_2$ phase and indicate heightened induced-dipole interactions compared to other hydrogen hydrates. △ Less

Submitted 23 May, 2024; originally announced May 2024.

Comments: 4 Figures

Thermodynamic properties of liquid mercury to 520 K and 7 GPa from acoustic velocity measurements

Authors: Simon Ayrinhac, Michel Gauthier, Livia E. Bove, Marc Morand, Gilles Le Marchand, Frédéric Bergame, Frédéric Decremps

Abstract: Ultrafast acoustics measurements on liquid mercury have been performed at high pressure and temperature in diamond anvils cell using picosecond acoustic interferometry. We extract the density of mercury from adiabatic sound velocities using a numerical iterative procedure. The pressure and temperature dependence of the thermal expansion, the isothermal compressibilty, the isothermal bulk modulus a… ▽ More Ultrafast acoustics measurements on liquid mercury have been performed at high pressure and temperature in diamond anvils cell using picosecond acoustic interferometry. We extract the density of mercury from adiabatic sound velocities using a numerical iterative procedure. The pressure and temperature dependence of the thermal expansion, the isothermal compressibilty, the isothermal bulk modulus and its pressure derivative are derived up to 7 GPa and 520 K. In the high pressure regime, the sound velocity values, at a given density, are shown to be only slightly dependent on the specific temperature and pressure conditions. The density dependence of sound velocity at low density is consistent with that observed with our data at high density in the metallic liquid state. △ Less

Submitted 23 October, 2013; originally announced October 2013.

Comments: 10 pages, 13 figures and 3 tables

Observation of a nanophase segregation in LiCl aqueous solutions from Transient Grating Experiments

Authors: L. E. Bove, C. Dreyfus, R. Torre, R. M. Pick

Abstract: Transient Grating experiments performed on supercooled LiCl, RH2O solutions with R>6 reveal the existence of a strong, short time, extra signal which superposes to the normal signal observed for the R=6 solution and other glass forming systems. This extra signal shows up below 190 K, its shape and the associated timescale depend only on temperature, while its intensity increases with R. We show th… ▽ More Transient Grating experiments performed on supercooled LiCl, RH2O solutions with R>6 reveal the existence of a strong, short time, extra signal which superposes to the normal signal observed for the R=6 solution and other glass forming systems. This extra signal shows up below 190 K, its shape and the associated timescale depend only on temperature, while its intensity increases with R. We show that the origin of this signal is a phase separation between clusters with a low solute concentration and the remaining, more concentrated, solution. Our analysis demonstrates that these clusters have a nanometer size and a composition which are rather temperature independent, while increasing R simply increases the number of these clusters. △ Less

Submitted 15 February, 2013; originally announced February 2013.

Comments: 19 pages+ 8 figures+ 2 tables

Ergodicity breaking in strong and network-forming glassy system

Authors: S. Caponi, M. Zanatta, A. Fontana, L. E. Bove, L. Orsingher, F. Natali, C. Petrillo, F. Sacchetti

Abstract: The temperature dependence of the non-ergodicity factor of vitreous GeO$_2$, $f_{q}(T)$, as deduced from elastic and quasi-elastic neutron scattering experiments, is analyzed. The data are collected in a wide range of temperatures from the glassy phase, up to the glass transition temperature, and well above into the undercooled liquid state. Notwithstanding the investigated system is classified… ▽ More The temperature dependence of the non-ergodicity factor of vitreous GeO$_2$, $f_{q}(T)$, as deduced from elastic and quasi-elastic neutron scattering experiments, is analyzed. The data are collected in a wide range of temperatures from the glassy phase, up to the glass transition temperature, and well above into the undercooled liquid state. Notwithstanding the investigated system is classified as prototype of strong glass, it is found that the temperature- and the $q$-behavior of $f_{q}(T)$ follow some of the predictions of Mode Coupling Theory. The experimental data support the hypothesis of the existence of an ergodic to non-ergodic transition occurring also in network forming glassy systems. △ Less

Submitted 24 September, 2008; originally announced September 2008.