Graeme J. Ackland
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View article: Distinction between ice phases VII, VIII, and X
Distinction between ice phases VII, VIII, and X Open
Ice phases VII, VIII, and X are all based on a body-centered cubic arrangement of molecules, the differences coming from how molecular orientation breaks the symmetry. It is debatable as to whether these should even be considered distinct …
View article: AIASSE—<i>Ab</i> <i>initio</i> augmented structure solving engine
AIASSE—<i>Ab</i> <i>initio</i> augmented structure solving engine Open
We have developed a hybrid methodology that self-consistently integrates empirical potential-based refinement of total scattering data with first-principles density functional theory-based molecular dynamics calculations. The aim is to pro…
View article: High-Tc 2D ambient BCS superconductors in hydrogenated transition-metal borides
High-Tc 2D ambient BCS superconductors in hydrogenated transition-metal borides Open
The discovery of MgB 2 , with T c of 39 K, has inspired intensive studies on various metal (di)-borides to identify other potential conventional high-temperature superconductors. A possible two-dimensional structure of metal borides with t…
View article: Pressure-driven electronegativity inversion in alkali liquids
Pressure-driven electronegativity inversion in alkali liquids Open
Liquid–liquid phase transitions (LLPTs) are typically characterized as two-state systems, where transitions occur between two distinct liquid phases driven by local structural rearrangements. In this study, we observed a continuous LLPT wi…
View article: Oscillation in the SIRS model
Oscillation in the SIRS model Open
We study the SIRS epidemic model, both analytically and on a square lattice. The analytic model has two stable solutions, post outbreak/epidemic (no infected, I=0) and the endemic state (constant number of infected: I>0). When the model is…
View article: Subcritical Determination of the Frenkel Line in Liquid Nitrogen, the Emergent Final Picture, and a Universal Equation for the Coordination Number of Real Fluids
Subcritical Determination of the Frenkel Line in Liquid Nitrogen, the Emergent Final Picture, and a Universal Equation for the Coordination Number of Real Fluids Open
We performed a series of neutron scattering experiments on deeply subcritical liquid nitrogen at 90 K (0.7TC). Our findings, when taken together with our previous results at 160 K (1.27TC) and 300 K (2.4TC), allow the Frenkel line phenomen…
View article: An Accurate Machine-Learned Potential for Krypton under Extreme Conditions
An Accurate Machine-Learned Potential for Krypton under Extreme Conditions Open
We have developed two machine-learned pair potentials for krypton based on CCSD(T) quantum chemical calculations on two and three atom clusters. Through extensive testing with molecular dynamics, we find both potentials give good agreement…
View article: Tadah! A Swiss Army Knife for Developing and Deployment of Machine Learning Interatomic Potentials
Tadah! A Swiss Army Knife for Developing and Deployment of Machine Learning Interatomic Potentials Open
The Tadah! code provides a versatile platform for developing and optimizing Machine Learning Interatomic Potentials (MLIPs). By integrating composite descriptors, it allows for a nuanced representation of system interactions, customized wi…
View article: Superconductivity of two-dimensional hydrogenated transition-metal diborides
Superconductivity of two-dimensional hydrogenated transition-metal diborides Open
Since the discovery of MgB2 with Tc=39K, various metal diborides of MB2 have been intensively studied to find possible conventional high-temperature superconductors. A possible 2D structure of the metal diboride has been shown to be in the…
View article: Two-gap superconductivity in a Janus MoSeLi monolayer
Two-gap superconductivity in a Janus MoSeLi monolayer Open
Two-dimensional (2D) lithium-decorated materials have emerged as a significant area of study since the prediction of superconductivity in lithium-decorated graphene at temperatures around 8.1 K, with experimental evidence observed at Tc = …
View article: Superconductivity and strain-enhanced phase stability of Janus tungsten chalcogenide hydride monolayers
Superconductivity and strain-enhanced phase stability of Janus tungsten chalcogenide hydride monolayers Open
Janus transition metal-dichalcogenide materials have attracted a great deal of attention due to their remarkable physical properties arising from the two-dimensional geometry and the breakdown of the out-of-plane symmetry. Using first-prin…
View article: Understanding solid nitrogen through molecular dynamics simulations with a machine-learning potential
Understanding solid nitrogen through molecular dynamics simulations with a machine-learning potential Open
We construct a fast, transferable, general purpose, machine-learning interatomic potential suitable for large-scale simulations of N2. The potential is trained only on high quality quantum chemical molecule-molecule interactions; no conden…
View article: Superconductivity in Janus IV-B transition metal chalcogenide hydrides
Superconductivity in Janus IV-B transition metal chalcogenide hydrides Open
Two-dimensional Janus transition-metal chalcogenide -hydrides (2D-JTMCs) feature a three layered structure, with a central layer of transition metal atoms, with chalcogenides below and hydogens above. This asymmetry endows 2D-JTMCs with un…
View article: Solid Solubility in Metallic Hydrogen
Solid Solubility in Metallic Hydrogen Open
Hydrogen in its metallic form is the most common material in our solar system, found under the extreme pressure and temperature conditions found in giant planets. Such conditions are inaccessible to experiment and consequently, theoretical…
View article: Organic compounds in metallic hydrogen
Organic compounds in metallic hydrogen Open
Metallic hydrogen[1] is the most common condensed material in the universe, comprising the centre of gas giant planets[2–4] However, experimental studies are extremely challenging[5–8], and most of our understanding of this material has be…
View article: Can the AMOEBA forcefield be used for high pressure simulations? The extreme case of methane and water
Can the AMOEBA forcefield be used for high pressure simulations? The extreme case of methane and water Open
We have performed classical molecular dynamics simulations using the fully polarizable Atomic Multipole Optimized Energetics for Biomolecular Applications (AMOEBA) forcefield implemented within the Tinker package to determine whether a mor…
View article: The re-entrant transition from the molecular to atomic phases of dense fluids: The case of hydrogen
The re-entrant transition from the molecular to atomic phases of dense fluids: The case of hydrogen Open
A simple phenomenological thermodynamic model is developed to describe the chemical bonding and unbonding in homonuclear diatomic systems. This model describes the entire phase diagram of dimer-forming systems and shows a transition from m…
View article: Understanding solid nitrogen through machine learning simulation
Understanding solid nitrogen through machine learning simulation Open
We construct a fast, transferable, general purpose, machine-learning interatomic potential suitable for large-scale simulations of $N_2$. The potential is trained only on high quality quantum chemical molecule-molecule interactions, no con…
View article: Combining models to generate consensus medium-term projections of hospital admissions, occupancy and deaths relating to COVID-19 in England
Combining models to generate consensus medium-term projections of hospital admissions, occupancy and deaths relating to COVID-19 in England Open
Mathematical modelling has played an important role in offering informed advice during the COVID-19 pandemic. In England, a cross government and academia collaboration generated medium-term projections (MTPs) of possible epidemic trajector…
View article: Superconductivity and electron self-energy in tungsten-sulfur-hydride monolayer
Superconductivity and electron self-energy in tungsten-sulfur-hydride monolayer Open
Hydrogen-rich structures have recently gained attention as a candidate for room-temperature superconductors. Hydrogen has high phonon frequencies and can be an ideal component for superconductors if it also exhibits strong electron–phonon …
View article: Experimental and computational study of the core-level crossing transition in iridium at high pressure
Experimental and computational study of the core-level crossing transition in iridium at high pressure Open
A core-level crossing (CLC) resulting from extreme compression has been calculated to occur in Ir metal at 80 GPa, analogous to a transition previously reported in Os at 392 GPa. We present results from static high-pressure diffraction exp…
View article: Isotopic Raman broadening due to Anderson localization of harmonic phonons in partially deuterated ice VII and VIII
Isotopic Raman broadening due to Anderson localization of harmonic phonons in partially deuterated ice VII and VIII Open
Raman spectra from molecular systems are typically regarded as comprising a set of sharp peaks. These arise from both single-molecule modes and extended $\\Gamma$ point phonons being, in theory, harmonic oscillators. Broadening is typicall…
View article: Combining models to generate consensus medium-term projections of hospital admissions, occupancy and deaths relating to COVID-19 in England
Combining models to generate consensus medium-term projections of hospital admissions, occupancy and deaths relating to COVID-19 in England Open
Mathematical modelling has played an important role in offering informed advice during the COVID-19 pandemic. In England, a cross government and academia collaboration generated Medium-Term Projections (MTPs) of possible epidemic trajector…
View article: Competition between superconductivity and molecularization in the quantum nuclear behavior of lanthanum hydride
Competition between superconductivity and molecularization in the quantum nuclear behavior of lanthanum hydride Open
Lanthanum hydride is the superconductor with the highest known critical temperature. It is believed that the superconductivity is of standard BCS type, with electrons forming Cooper pairs and opening the superconducting band gap. Here, we …
View article: A comparison of different Fourier transform procedures for analysis of diffraction data from noble gas fluids
A comparison of different Fourier transform procedures for analysis of diffraction data from noble gas fluids Open
A comparison is made between the three principal methods for the analysis of neutron and x-ray diffraction data from noble gas fluids by direct Fourier transform. All three methods (standard Fourier transform, Lorch modification, and Soper…
View article: H<sub>2</sub> Chemical Bond in a High-Pressure Crystalline Environment
H<sub>2</sub> Chemical Bond in a High-Pressure Crystalline Environment Open
We show that the hydrogen in metal superhydride compounds can adopt two distinct states-atomic and molecular. At low pressures, the maximum number of atomic hydrogens is typically equal to the valency of the cation; additional hydrogens pa…
View article: Enhancing the stability of the <i>ω</i> phase of zirconium alloys via local interlayer twists
Enhancing the stability of the <i>ω</i> phase of zirconium alloys via local interlayer twists Open
The addition of solute provides an effective means to alter the stability of phases in metallic materials. This is particularly true for the metastable ω phase in Tiand Zr-based alloys, however, the underlying mechanism remains inconclusiv…