UKAEA Journals

Showing 1 - 10 of 23 Journals Results
2021
UKAEA-CCFE-PR(21)54

The concept of elastic dipole tensor of a defect is generalised to enable the treatment of lattice distortions, produced by defects at elevated temperatures. Thermodynamic and statistical mechanics derivations show the feasibility of computing the formation free energy and finite-temperature elastic dipole tensor of a $frac{1}{2}langle 111 rangle$ …

Preprint Published
2020
UKAEA-CCFE-PR(20)141

Using ab initio density function theory calculations, we have determined the structure of self-interstitial atom (SIA) defects in the most commonly occurring face-centred cubic (FCC) metals. The most stable SIA defects in Al, Ca, Ni, Cu, Pd and Ag are the {100} dumbbells whereas octahedral SIA configurations have the lowest energy in Pt, R…

Preprint Published
2020
UKAEA-CCFE-PR(20)108

We performed ab initio density functional theory simulations of 1/2{111} interstitial dislocation loops, closed and open vacancy loops, {100} interstitial loops and voids in tungsten, using simulation cells involving from 2000 to 2700 atoms. The size of the loops transcends the microscopic scale and reaches the mesoscopic scale where as…

Preprint Published
2020
UKAEA-CCFE-PR(20)103

We develop a dynamic model for the evolution of an ensemble of hundreds of interacting irradiation-induced mobile nanoscale defects in a micrometre size sample. The model uses a Langevin defect dynamics approach coupled to a finite element model, treated using the superposition method. The elastic field of each defect is described by its elastic…

Preprint
2020
UKAEA-CCFE-PR(19)15

Vacancy formation and migration control self-diffusion in pure crystalline materials, whereas irradiation produces high concentrations of vacancy and self-interstitial atom defects, exceeding by many orders of magnitude the thermal equilibrium concentrations. The defects themselves, and the extended dislocation microstructure formed under irradi…

Preprint Published
2020
UKAEA-CCFE-PR(19)06

For several decades, the striking contradiction between the Huang diffuse scattering experiments, resistivity recovery data, and predictions derived from density functional theory (DFT) remained one of the mysteries of defect physics in molybdenum. Since the nineteen seventies, observations of Huang X-ray diffuse scattering appeared to indicate …

Preprint Published
2019
UKAEA-CCFE-PR(19)40

CALANIE (CALculation of ANIsotropic Elastic energy) program evaluates an elastic interaction correction to the total energy of a localized object, for example a defect in a solid material simulated using an {it ab initio} or molecular statics approach, resulting from the use of periodic boundary conditions. The correction, computed using a fully el…

Preprint Purchase
2018
UKAEA-CCFE-PR(18)83

Magnetic plasma confinement is a key element of fusion tokamak power plant design, yet changes in magnetic properties of alloys and steels occurring under neutron irradiation are often overlooked. We perform a quantitative study exploring how irradiation-induced precipitation affects magnetic properties of Fe-Cr alloys. Magnetic properties are simu…

Preprint Published
2017
CCFE-PR(17)69

Density functional theory (DFT) calculations show that self-interstitial atom defects in nonmagnetic body-centred cubic (bcc) metals adopt strongly anisotropic configurations, elongated in the h111i direction1–4. Elastic distortions, associated with such anisotropic defect configurations, appear similar to the distortions around small prismatic d…

Preprint Purchase
2016

Spin–lattice dynamics generalizes molecular dynamics to magnetic materials, where dynamic variables describing an evolving atomic system include not only coordinates and velocities of atoms but also directions and magnitudes of atomic magnetic moments (spins). Spin–lattice dynamics simulates the collective time evolution of spins and atoms, tak…

Published