Publications by Richard Gaal | EPFL Graph Search

Related publications (49)

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

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

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

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

Calibration of optical tweezers with non-spherical probes via high-resolution detection of Brownian motion

László Forró, Richard Gaal, Sylvia Jeney, Flavio Maurizio Mor

Optical tweezers are commonly used and powerful tools to perform force measurements on the piconewton scale and to detect nanometer-scaled displacements. However, the precision of these instruments relies to a great extent on the accuracy of the calibratio ...

Elsevier Science Bv2015

Electrical property measurements of Cr-N codoped TiO2 epitaxial thin films grown by pulsed laser deposition

László Forró, Arnaud Magrez, Richard Gaal, Jacim Jacimovic

The temperature dependent resistivity and thermo-electric power of Cr-N codoped TiO2 were compared with that of single element N and Cr doped and undoped TiO2 using epitaxial anatase thin films grown by pulsed laser deposition on (100) LaAlO3 substrates. T ...

AIP American Institute of Physics2013

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

Quantum versus classical protons in pure and salty ice under pressure

Richard Gaal, Livia Eleonora Bove Kado

It is generally accepted that nuclear quantum effects (NQEs) trigger the transition to the nonmolecular form of ice under increasing pressure. This picture is challenged in salty ice, where Raman scattering measurements up to 130 GPa of molecular ice VII c ...

Amer Physical Soc2016

From nanotubes to single crystals: Co doped TiO2

Helmuth Berger, László Forró, Arnaud Magrez, Bálint Náfrádi, Endre Horvath, Richard Gaal, Jacim Jacimovic, Neda Nikseresht Ghanepour

Millimeter-sized cobalt doped rutile crystals with a bi-pyramidal shape are obtained by chemical vapour transport using scroll-type H2Ti3O7 nanotubes as a precursor in which Co2+ ions are introduced by a simple ion exchange method prior to the growth. Desp ...

Amer Inst Physics2013

Single crystals of superconducting SmFeAsOHx: Structure and properties

László Forró, Alla Arakcheeva, Richard Gaal, Sergiy Katrych, 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, Bálint Náfrádi, Richard Gaal, Sergiy Katrych, Péter Szirmai, Andrea Pisoni

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

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

Philippe Gillet, Richard Gaal, 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

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

Magnetotransport studies of superconducting Pr4Fe2As2Te1-xO4

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

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

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

Henrik Moodysson Rønnow, Ivica Zivkovic, Richard Gaal, Wen Hua Bi, 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

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

Philippe Gillet, Richard Gaal, 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

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

Henrik Moodysson Rønnow, Ivica Zivkovic, Richard Gaal, 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

Matthiessen's rule in MgB2: Resistivity and T-c as a function of point defect concentration

László Forró, Richard Gaal, Neven Barisic, Balazs Sipos

We present the results of a systematic study of the temperature-dependent resistivity and of T-c of a single crystal MgB2 sample as a function of point defect concentration. We have found linear, albeit weak, correlation between the decreasing superconduct ...

2007