A5005837258- Fusion materials and technologies
- Nuclear Materials and Properties
- Electron and X-Ray Spectroscopy Techniques
- Microstructure and mechanical properties
- Ion-surface interactions and analysis
- Crystallography and Radiation Phenomena
- Microstructure and Mechanical Properties of Steels
- Advanced Chemical Physics Studies
- High-pressure geophysics and materials
- Advanced Materials Characterization Techniques
- Magnetic properties of thin films
- Theoretical and Computational Physics
- Advanced Electron Microscopy Techniques and Applications
- Nuclear reactor physics and engineering
- High Temperature Alloys and Creep
- X-ray Diffraction in Crystallography
- Surface and Thin Film Phenomena
- Intermetallics and Advanced Alloy Properties
- Nuclear materials and radiation effects
- Magnetic Properties and Applications
- Advanced materials and composites
- Hydrogen embrittlement and corrosion behaviors in metals
- X-ray Spectroscopy and Fluorescence Analysis
- Physics of Superconductivity and Magnetism
- Nuclear Physics and Applications
Culham Science Centre
2015-2024
Culham Centre for Fusion Energy
2015-2024
United Kingdom Atomic Energy Authority
2014-2024
University of Oxford
1999-2023
Imperial College London
2007-2023
Thomas Young Centre
2019-2023
Institute of History
2022
Pedagogical University
2020-2021
Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas
2021
Armavir State Pedagogical Academy
2020-2021
We demonstrate how by taking better account of electron correlations in the $3d$ shell metal ions nickel oxide it is possible to improve description both energy loss spectra and parameters characterizing structural stability material compared with local spin density functional theory.
We investigate the structure and mobility of single self-interstitial atom vacancy defects in body-centered-cubic transition metals forming groups 5B (vanadium, niobium, tantalum) 6B (chromium, molybdenum, tungsten) Periodic Table. Density-functional calculations show that all these axially symmetric ⟨111⟩ configuration has lowest formation energy. In chromium, difference between energies ⟨110⟩ configurations is very small, making two structures almost degenerate. Local densities states for...
We present an investigation of systematic trends for the self-interstitial atom (SIA) defect behavior in body-centered cubic (bcc) transition metals using density-functional calculations. In all nonmagnetic bcc most stable SIA configuration has $⟨111⟩$ symmetry. Metals group 5B periodic table (V, Nb, Ta) have significantly different energies formation and $⟨110⟩$ configurations, while 6B (Cr, Mo, W) two configurations are linked by a soft bending mode. The relative defects fundamentally from...
We have developed empirical interatomic potentials for studying radiation defects and dislocations in tungsten. The use the embedded atom method formalism are fitted to a mixed database, containing various experimentally measured properties of tungsten ab initio formation energies defects, as well forces computed random liquid configurations. availability data on atomic force fields proves critical development new potentials. Several point extended defect configurations were used test...
Atomic collision processes are fundamental to numerous advanced materials technologies such as electron microscopy, semiconductor processing and nuclear power generation. Extensive experimental computer simulation studies over the past several decades provide physical basis for understanding atomic-scale occurring during primary displacement events. The current international standard quantifying this energetic particle damage, Norgett-Robinson-Torrens displacements per atom (NRT-dpa) model,...
Abstract The high-energy, high-intensity neutron fluxes produced by the fusion plasma will have a significant life-limiting impact on reactor components in both experimental and commercial devices. As well as producing defects, neutrons bombarding materials initiate nuclear reactions, leading to transmutation of elemental atoms. Products many these reactions are gases, particularly helium, which can cause swelling embrittlement materials. This paper integrates several different computational...
Recent experiments on in situ high-energy self-ion irradiation of tungsten (W) show the occurrence unusual cascade damage effects resulting from single-ion impacts, shedding light nature radiation expected components a fusion reactor. In this paper, we investigate dynamics defect production 150 keV collision cascades W at atomic resolution, using molecular-dynamics simulations and comparing predictions with experimental observations. We that exhibit no subcascade break-up even high energies,...
Abstract The influence of Mott-Hubbard electron-electron correlations on the electronic structure and structural stability uranium dioxide (UO2) has been analysed using local spin-density approximation (LSDA) + U approach. We have found that inclusion a term describing Hubbard on-site repulsion between 5f electrons results in dramatic improvement description equilibrium magnetic UO2 for which conventional LSDA calculations incorrectly predict non-magnetic metallic ground state. presence band...
We develop a semi-empirical many-body interatomic potential suitable for large scale molecular dynamics simulations of magnetic α-iron. The functional form the embedding part is derived using combination Stoner and Ginzburg–Landau models. show that it symmetry broken solutions model describing spontaneous magnetization atoms provide link between magnetism forces. discuss range applications new method.
We compare experimentally observed electron energy loss spectra (EELS) of uranium dioxide UO2 and nickel monoxide NiO with the results ab-initio calculations carried out by using a method combining local spin density approximation Hubbard U term (the LSDA + method). show that taking better account strong Coulomb correlations between electrons in 5f shell ions 3d it is possible to arrive at description spectra, cohesive energies elastic constants both oxides compared functional theory. For we...
Debye–Waller factors and absorptive scattering are given of 44 elemental crystals over the temperature range from 1 to 1000 K or melting temperature, whichever is smaller. The derived experimentally determined phonon density states accuracy these typically 2 3%. Necessary data have also been compiled for an additional 22 which characteristic Debye temperatures known. These can be used estimate factor at any using analytical expression states.
Body-centered-cubic iron develops an elastic instability, driven by spin fluctuations, near the $\ensuremath{\alpha}\ensuremath{-}\ensuremath{\gamma}$ phase transition temperature ${T}_{c}=912\text{ }\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$ that is associated with dramatic reduction of shear stiffness constant ${c}^{\ensuremath{'}}=({c}_{11}\ensuremath{-}{c}_{12})/2$ ${T}_{c}$. This ${c}^{\ensuremath{'}}$ has a profound effect on dependence anisotropic self-energies dislocations in...
A robust algorithm and computer program have been developed for the parameterization of elastic absorptive electron atomic scattering factors. The is based on a combined modified simulated-annealing least-squares method, works well fitting both factors with five Gaussians. As an application this program, parameterized all neutral atoms s up to 6 Å−1. Error analysis shows that present results are considerably more accurate than previous analytical fits in terms mean square value deviation...
We develop a dynamical simulation model for magnetic iron where atoms are treated as classical particles with intrinsic spins. The interact via scalar many-body forces well spin orientation dependent of the Heisenberg form. coupling between lattice and degrees freedom is described by coordinate-dependent exchange function proportional to gradient this function. spin-lattice dynamics approach extends existing potential treatment case energy interaction depends on relative noncollinear...
The structure and phase stability of binary tungsten-vanadium tungsten-tantalum alloys are investigated over a broad range alloy compositions using ab initio cluster expansion methods. characterized by the negative enthalpy mixing across entire composition range. Complex intermetallic compounds predicted calculations as lowest energy structures for both alloys. effect atomic relaxation on is almost negligible in W-V, but substantial W-Ta Canonical Monte Carlo simulations used predicting...
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....
Under the anticipated operating conditions for demonstration magnetic fusion reactors beyond ITER, structural and plasma-facing materials will be exposed to unprecedented of irradiation, heat flux, temperature. While such extreme environments remain inaccessible experimentally, computational modeling simulation can provide qualitative quantitative insights into response complement available experimental measurements with carefully validated predictions. For components as first wall divertor,...
Using in-situ transmission electron microscopy, we have directly observed nano-scale defects formed in ultra-high purity tungsten by low-dose high energy self-ion irradiation at 30K. At cryogenic temperature lattice reduced mobility, so these microscope observations offer a window on the initial, primary damage caused individual collision cascade events. Electron images provide direct evidence for power-law size distribution of high-energy cascades, with an upper limit independent incident...
Density functional theory models developed over the past decade provide unique information about structure of nanoscale defects produced by irradiation and nature short-range interaction between radiation defects, clustering their migration pathways. These ab initio models, involving no experimental input parameters, appear to be as quantitatively accurate informative most advanced techniques for observation damage phenomena. have effectively created a new paradigm scientific investigation...