A5053894223- High-pressure geophysics and materials
- Nuclear Materials and Properties
- Fusion materials and technologies
- Microstructure and Mechanical Properties of Steels
- Advanced Chemical Physics Studies
- High Temperature Alloys and Creep
- Theoretical and Computational Physics
- Physics of Superconductivity and Magnetism
- Magnetic Properties and Applications
- nanoparticles nucleation surface interactions
- Organic and Molecular Conductors Research
- Material Dynamics and Properties
- Geological and Geochemical Analysis
- Advanced Materials Characterization Techniques
- Conducting polymers and applications
- Glass properties and applications
- X-ray Diffraction in Crystallography
- Organic Light-Emitting Diodes Research
- Organic Electronics and Photovoltaics
- Hydrogen embrittlement and corrosion behaviors in metals
- Microstructure and mechanical properties
- Rare-earth and actinide compounds
- Molecular Junctions and Nanostructures
- Methane Hydrates and Related Phenomena
- Diamond and Carbon-based Materials Research
Culham Science Centre
2014-2024
United Kingdom Atomic Energy Authority
2014-2024
Culham Centre for Fusion Energy
2005-2023
Université Paris-Saclay
2022
Commissariat à l'Énergie Atomique et aux Énergies Alternatives
2022
CEA Paris-Saclay
2022
Schlumberger (British Virgin Islands)
2019
Abingdon Community Hospital
2019
University of Bristol
2001-2007
Nikolaev Institute of Inorganic Chemistry
1989-2007
The phase stability of fcc and bcc magnetic binary Fe-Cr, Fe-Ni, Cr-Ni alloys, ternary Fe-Cr-Ni alloys is investigated using a combination density functional theory (DFT), cluster expansion (CE), (MCE) approaches. Energies, moments, volumes more than 500 alloy structures have been evaluated DFT, the predicted most stable configurations are compared with experimental observations. Deviations from Vegard law in resulting nonlinear variation atomic moments as functions composition, observed....
Iron-chromium alloys are characterized by a complex phase diagram, the small negative enthalpy of mixing at low Cr concentrations in bcc $\ensuremath{\alpha}$-phase Fe, and inversion short-range order parameter. We present Monte Carlo simulations binary Fe-Cr alloy based on cluster expansion approximation for system. The set coefficients is validated against density functional calculations energies clusters chromium structure. show that limit concentration remains up to fairly high...
An ab initio-based magnetic-cluster-expansion treatment developed for body- and face-centered cubic phases of iron iron-chromium alloys is applied to modeling the $\ensuremath{\alpha}\text{\ensuremath{-}}\ensuremath{\gamma}$ $\ensuremath{\gamma}\text{\ensuremath{-}}\ensuremath{\delta}$ phase transitions in these materials. The Curie, N\'eel, structural phase-transition temperatures predicted by model are good agreement with experimental observations, indicating that it thermal excitation...
A model lattice ab initio parameterized Heisenberg-Landau magnetic cluster expansion Hamiltonian spanning a broad range of alloy compositions and large variety chemical configurations has been developed for face-centered cubic Fe-Ni alloys. The thermodynamic properties the alloys are explored using configuration Monte Carlo simulations over temperature extending well 1000 K. predicted cubic-body-centered coexistence curve, phase stability ordered Fe3Ni, FeNi, FeNi3 intermetallic compounds,...
To understand the behaviour of irradiated defects and kinetic pathways micro-structural evolution in Fe–Cr alloys, we use a combination density functional theory with statistical approaches involving cluster expansions Monte Carlo simulations. A lowest negative mixing enthalpy is found at 6.25% Cr that consistent our DFT prediction an ordered Fe15Cr structure. At 50% Cr, it predicted formation 4 times smaller than calculated by CPA approach. Thermodynamic precipitation properties are then...
Noncollinear configurations of local magnetic moments at Fe/Cr interfaces in Fe-Cr alloys are explored using a combination density functional theory (DFT) and cluster expansion (MCE) simulations. We show that frustration can be partially resolved through the formation noncollinear structures, which occur not only stepped but also smooth interfaces, for example (110) interface where noncollinearity predicted by simulations is observed experimentally. Both DFT MCE predict magnetically...
Self-ion irradiation of pure tungsten with 2 MeV W ions provides a way simulating microstructures generated by neutron in components fusion reactor. Transmission electron microscopy (TEM) has been used to characterize defects formed samples ion irradiation. It was found that irradiated 0.85 dpa at relatively low temperatures develops characteristic microstructure dominated dislocation loops and black dots. The density size distribution these were estimated. Some the exposed self-ion then...
We investigate phase stability and vacancy formation in fcc Fe-Ni alloys over a broad composition-temperature range, via density functional theory parametrized effective interaction model, which includes explicitly spin chemical variables. On-lattice Monte Carlo simulations based on this model are used to predict the temperature evolution of magnetochemical phase. The experimental composition-dependent Curie order-disorder transition temperatures successfully predicted. point out significant...
We describe the parameterization of a tungsten-hydrogen empirical potential designed for use with large-scale molecular dynamics simulations highly irradiated tungsten containing hydrogen isotope atoms, and report test results. Particular attention has been paid to getting good elastic properties, including relaxation volumes small defect clusters, interaction energy between isotopes typical irradiation-induced defects in tungsten. conclude that ordering changes ratio H atoms point defects,...
We discuss how two techniques, based on (1) lattice statics/lattice dynamics simulations and (2) Monte Carlo methods may be used to calculate the thermodynamic properties of oxide mixtures at zero high pressure. The calculations involve a full free energy structural optimization each number configurations, followed by averaging. Strategies for generating suitable set configurations are discussed. compare results obtained random generation with those using radial distribution functions or...
Tungsten, given its high heat and neutron resistance, is often the material of choice for plasma-facing components in nuclear fusion reactors. However, understanding predicting behavior hydrogen isotopes (deuterium tritium) within tungsten's lattice poses a significant challenge. The retention diffusion these isotopes, which are influenced by microstructural defects such as vacancies, can significantly impact performance safety devices. This article employs Large-scale Atomic/Molecular...
The two-state molecular orbital model of the one-dimensional phenyl-based semiconductors is applied to poly(para-phenylene vinylene). energies low-lying excited states are calculated using density matrix renormalization group method. Calculations both exciton size and charge gap show that there ${}^{1}{B}_{u}^{\ensuremath{-}}$ ${}^{1}{A}_{g}^{+}$ excitonic levels below band threshold. energy ${1}^{1}{B}_{u}^{\ensuremath{-}}$ extrapolates 2.60 eV in limit infinite polymers, while...
A range of methods, based on Monte Carlo and lattice dynamics simulations, are presented for the calculation thermodynamic properties solid solutions phase diagrams. These include simulations with explicit interchange cations, use semigrand-canonical ensemble configurational bias techniques, hybrid Carlo/molecular dynamics, a new technique. It is crucial to take account relaxation local atomic environment vibrational effects. Examples studied (i) enthalpy entropy mixing, diagram spinodal...
We present density-matrix renormalization-group calculations of the Pariser-Parr-Pople-Peierls model linear polyenes within adiabatic approximation. calculate vertical and relaxed transition energies, geometries for various excitations on long chains. The triplet $(1{}^{3}{B}_{u}^{+})$ even-parity singlet $(2{}^{1}{A}_{g}^{+})$ states have a 2-soliton 4-soliton forms, respectively, both with large relaxation energies. dipole-allowed $(1{}^{1}{B}_{u}^{\ensuremath{-}})$ state forms an...
We present a combined experimental and computational study of high temperature magnetic properties Fe–Cr alloys with chromium content up to about 20 at.%. The cluster expansion method is applied model the random alloys, in particular Curie transition temperature, as function alloy composition. find that at low (3–6 at.%) Cr increases increase concentration. It maximum approximately 6 at.% then decreases for higher content. same feature found thermo-magnetic measurements performed on where 5...
A Magnetic Cluster Expansion model for ternary face-centered cubic Fe-Ni-Cr alloys has been developed, using DFT data spanning binary and alloy configurations. Using this Hamiltonian, we perform Monte Carlo simulations explore magnetic structures of over the entire range compositions, considering both random ordered structures. In alloys, removal collinearity constraint reduces total moment but does not affect predicted compositions where adopt low-temperature ferromagnetic During alloying...
We show how Monte Carlo simulations with the explicit interchange of cations, semigrand-canonical ensemble and configurational bias techniques, can be used to calculate phase diagrams for oxides, including both solid liquid phases. illustrate our approach system CaO/MgO where techniques take full account local structural distortion clustering due large mismatch between sizes two cations. All characteristic features MgO/CaO diagram, eutectic point regions liquid−solid coexistence, are reproduced.
We show how a configurational lattice dynamics technique, in which the free energy of number configurations is determined directly by means fully dynamic structural minimization, can be used to calculate thermodynamic properties solid solutions and phase diagrams. No assumptions are made as nature solution both vibrational entropy contributions directly. Only small required. illustrate method using MnO/MgO, for our results support recent experiments Wood, Hackler, Dobson [Contrib. Mineral....