Publications by Richard Gaal | EPFL Graph Search

Author Correction: Structural phase transition in NH4F under extreme pressure conditions

In the Acknowledgements section the following sentence was added: We acknowledge the European Synchrotron Radiation Facility for provision of synchrotron radiation facilities, and we would like to thank Michael Hanfland and Mohamed Mezouar for assistance i ...

Springer Science and Business Media LLC2025

Hydrogen Hydrates Under Extreme Conditions: Insights Into High-pressure Phases and Implications for Planetary Interiors

Richard Gaal, Livia Eleonora Bove Kado, Tomasz Poreba

Hydrogen hydrates, formed from hydrogen and water under high-pressure and low-temperature conditions, exhibit a rich phase behavior governed by intricate intermolecular interactions. Their structural evolution under extreme conditions provides a unique pla ...

AMER PHYSICAL SOC2025

Observation of plastic ice VII by quasi-elastic neutron scattering

Richard Gaal, Livia Eleonora Bove Kado, Maria Rescigno

Water is the third most abundant molecule in the universe and a key component in the interiors of icy moons, giant planets and Uranus- and Neptune-like exoplanets1, 2–3. Owing to its distinct molecular structure and flexible hydrogen bonds that readily ada ...

2025

Bullet pressure-cell design for neutron scattering experiments with horizontal magnetic fields and dilution temperatures

Richard Gaal, Henrik Moodysson Rønnow, Luc Testa, Gaétan Charles Antoine Giriat, Ellen Fogh, Jana Pásztorová

The simultaneous application of high magnetic fields and high pressures for controlling magnetic ground states is important for testing our understanding of many-body quantum theory. However, the implementation for neutron scattering experiments presents a ...

2025

Cavity-magnon-polariton spectroscopy of strongly hybridized electro-nuclear spin excitations in LiHoF4

Richard Gaal, Henrik Moodysson Rønnow, Ivica Zivkovic, Peter Babkevich

We first present a formalism that incorporates the input-output formalism and the linear response theory to employ cavity-magnon-polariton coupling as a spectroscopic tool for investigating strongly hybridized electro-nuclear spin excitations. A microscopi ...

Nature Research2024

Structural phase transition in NH₄F under extreme pressure conditions

Richard Gaal

Ammonium fluoride (NH₄F) exhibits a variety of crystalline phases depending on temperature and pressure. By employing Raman spectroscopy and synchrotron X-ray diffraction beyond megabar pressures (up to 140 GPa), we have here observed a novel dense solid p ...

2024

Large-cage occupation and quantum dynamics of hydrogen molecules in sII clathrate hydrates

Richard Gaal, Livia Eleonora Bove Kado, Umbertoluca Ranieri

Hydrogen clathrate hydrates are ice-like crystalline substances in which hydrogen molecules are trapped inside polyhedral cages formed by the water molecules. Small cages can host only a single H-2 molecule, while each large cage can be occupied by up to f ...

Aip Publishing2024

Giant Splitting of the Hydrogen Rotational Eigenenergies in the C2 Filled Ice

Richard Gaal

Hydrogen hydrates exhibit a rich phase diagram influenced by both pressure and temperature, with the so-called C2 phase emerging prominently above 2.5 GPa. In this phase, hydrogen molecules are densely packed within a cubic icelike lattice and the interact ...

2024

Pressure dependence of superconducting properties of layered BaNi2P2

Richard Gaal, Henrik Moodysson Rønnow, Ivica Zivkovic, Youngro Lee

The discovery of unconventional superconductivity in a broad class of iron-based materials invoked extensive research on the corresponding compounds of other transition metals. For instance, BaNi2P2 exhibits a superconducting transition with a critical tem ...

Elsevier2023

Observation of the most H2-dense filled ice under high pressure

Richard Gaal, Livia Eleonora Bove Kado, Lorenzo Monacelli, Maria Rescigno

Hydrogen hydrates are among the basic constituents of our solar system's outer planets, some of their moons, as well Neptune-like exo-planets. The details of their high-pressure phases and their thermodynamic conditions of formation and stability are funda ...

National Academy of Sciences2023

Structure, heat capacity and Raman spectra of Ba2MgWO6 single crystals grown in BaCl2-MgCl2 flux

Richard Gaal, Henrik Moodysson Rønnow, Ivica Zivkovic, Jana Pásztorová

We present a new method of Ba2MgWO6 single crystal synthesis that allows to grow larger crystals using a BaCl2 and MgCl2 flux. Difficulties to grow single crystals of a size suitable for macroscopic material property measurements caused the majority of cha ...

ACADEMIC PRESS INC ELSEVIER SCIENCE2023

Diffusion in dense supercritical methane from quasi-elastic neutron scattering measurements

Richard Gaal

Methane, the principal component of natural gas, is an important energy source and raw material for chemical reactions. It also plays a significant role in planetary physics, being one of the major constituents of giant planets. Here, we report measurement ...

Nature Research2021

White-line evolution in shocked solid Ta evidenced by synchrotron x-ray absorption spectroscopy

Richard Gaal

Time-resolved x-ray absorption experiments have been performed on shocked tantalum. Using a single 100 ps synchrotron x-ray pulse, nanosecond-lived equilibrium states of shocked solid Ta have been measured by L-3-edge absorption spectroscopy. The energy sh ...

2020

Observation of methane filled hexagonal ice stable up to 150 GPa

Richard Gaal, Philippe Gillet, Livia Eleonora Bove Kado, Umbertoluca Ranieri

Gas hydrates consist of hydrogen-bonded water frameworks enclosing guest gas molecules and have been the focus of intense research for almost 40 y, both for their fundamental role in the understanding of hydrophobic interactions and for gas storage and ene ...

National Academy of Sciences2019

Quantum Dynamics of H-2 and D-2 Confined in Hydrate Structures as a Function of Pressure and Temperature

Richard Gaal, Philippe Gillet, Livia Eleonora Bove Kado, Umbertoluca Ranieri

We present an extensive study of the quantum dynamics of molecular hydrogen trapped within the nanocavities of two hydrate structures at low temperatures, namely, clathrate structure II and filled ice structure Cl. By inelastic neutron scattering measureme ...

AMER CHEMICAL SOC2019

Orientational Ordering, Locking-in, and Distortion of CH4 Molecules in Methane Hydrate III under High Pressure

Richard Gaal, Philippe Gillet, Livia Eleonora Bove Kado, Umbertoluca Ranieri

2018

Cyan titania nanowires: Spectroscopic study of the origin of the self-doping enhanced photocatalytic activity

László Forró, Richard Gaal, Arnaud Magrez, Alla Arakcheeva, Bálint Náfrádi, Xavier Berdat, Jacim Jacimovic, Massimo Spina, Endre Horvath, Laurent Syavoch Bernard, Péter Szirmai

We report a detailed spectroscopic study of Ti3+ self-doped TiO2 nanowires prepared by high temperature annealing of the protonated titanate nanowires (TiONW) in hydrogen atmosphere. Hydrogenation causes a color change from white to cyan and a major increa ...

Elsevier2017

Single crystals of superconducting SmFeAsOHx: Structure and properties

László Forró, Richard Gaal, Alla Arakcheeva, Sergiy Katrych, Janusz Andrzej Karpinski, Andrea Pisoni, Ping Huang, Péter Krisztián Matus

We report the synthesis, structure, and superconducting properties of single crystals of SmFeAsOHx. The crystals were grown at high pressure and high temperature using a cubic anvil technique. H-1-NMR studies confirm the presence of H atoms in the samples. ...

Amer Physical Soc2016

Upper critical field, pressure-dependent superconductivity and electronic anisotropy of Sm4Fe2As2Te1-xO4-yFy

László Forró, Richard Gaal, Bálint Náfrádi, Sergiy Katrych, Janusz Andrzej Karpinski, Andrea Pisoni, Péter Szirmai

We present a detailed study of the electrical transport properties of a recently discovered iron-based superconductor: Sm4Fe2As2Te0.72O2.8F1.2. We followed the temperature dependence of the upper critical field by resistivity measurement of single crystals ...

Iop Publishing Ltd2016

Magnetotransport studies of superconducting Pr4Fe2As2Te1-xO4

László Forró, Richard Gaal, Bálint Náfrádi, Sergiy Katrych, Janusz Andrzej Karpinski, Andrea Pisoni, Péter Szirmai

We report a study of the electrical transport properties of single crystals of Pr(4)Fe(2)As(2)Te(1-)xO(4), a recently discovered iron-based superconductor. Resistivity, Hall effect, and magnetoresistance are measured in a broad temperature range revealing ...

Amer Physical Soc2016