Atomistic simulation of collision cascades in zircon (original) (raw)
Related papers
Molecular dynamics simulation of defect production in collision cascades in zircon
NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS, 2005
Defect production in collision cascades in zircon has been examined by molecular dynamics simulations using a partial charge model combined with the Ziegler-Biersack-Littmark potential. U, Zr, Si and O recoils with energies ranging from 250 eV to 5 keV were simulated in the NVE ensemble. To obtain good statistics, 5-10 cascades in randomly chosen directions were simulated for each ion and energy. The damage consists of mainly Si and O Frenkel pairs, a smaller number of Zr Frenkel pairs, and Zr on Si antisite defects. Defect production, interstitial clustering, ion beam mixing and Si-O-Si polymerization increase with PKA mass and energy.
Amorphization in zircon: evidence for direct impact damage
Journal of Physics: Condensed Matter, 2000
X-ray diffraction has been used to characterize the amorphous phase present in a series of radiation-damaged natural zircons with radiation doses ranging from 0.06 to 16 × 10 18 α-decay events g −1 . The fraction of amorphous material present in each of the samples studied has been determined, and its dependence on the radiation dose has been calibrated. Direct determination of the amorphous fraction confirms that amorphization in natural zircon occurs as a consequence of the direct impact within cascades caused by α-recoil nuclei. These results are not consistent with the commonly accepted double-overlap model of damage accumulation.
MRS Proceedings, 2013
Molecular dynamics simulations are performed to investigate the defect accumulation and microstructure evolution in hcp zirconium (Zr) -a material which is widely used as clad for nuclear fuel. Cascades are generated with a 3 keV primary knock-on atom (PKA) using an embedded atom method (EAM) potential with interactions modified for distances shorter than 0.1 Å. With sequential cascade simulations we show the emergence of stacking faults both in the basal and prism planes, and a Shockley partial dislocation on the basal plane.
An interatomic potential for simulation of defects and phase change of zirconium
We introduce a long-range interaction analytical embedded atom method (namely la-EAM) interatomic potential, which has been developed by fitting the lattice constants, cohesive energy, mono-vacancy formation energy and elastic constants of a-Zirconium. We validate this la-EAM potential by extensive investigation of the bulk, surface, and defect properties of Zirconium using molecular dynamics simulations compared with available experiments and theoretical results. We examine the lattice constants, cohesive energy, elastic constants, phonon dispersion curves of a-, band nd x-Zirconium and find a good agreement with available experiments. We have studied the 0D (zero-dimension) defects including vacancies and self-interstitial atoms, 1D defects (dislocations), 2D defects including surface and stacking fault, and 3D bulk properties. Furthermore, our phase transformation energy barrier of a ? x agrees with the experimental observation. The success of our potential could attribute to the correctly accounting for the long-range interactions of the Zr atoms. Our results suggest that the developed la-EAM potential of Zr is useful in molecular dynamics simulations of bulk, surface and defect properties and phase transitions of Zirconium at various temperatures and pressures.
A model study of displacement cascades distributions in zirconium
Journal of Nuclear Materials, 2005
5 to 200 keV displacement cascades in zirconium are studied in the binary collision approximation with the simulation code Marlowe. The cascades are analysed statistically by means of component analysis, fuzzy clustering and isodata analysis. As a consequence of the large recoil ranges and range straggling specific to open hcp lattices like Zr, a large dispersion of the frequencies of Frenkel pair distributions is found, as well as of the spatial extent and morphology of vacancy and interstitial distributions. In Zr, cascades are formed by a widespread distribution of displacement clusters that can be small. Remarkably, the size and morphology distributions of these clusters are found independent of the primary recoil energy in the energy range investigated.
Nuclear Engineering and Technology, 2018
In this article, we conducted molecular dynamics simulations to investigate the effect of applied strain and temperature on irradiation-induced damage in alpha-zirconium. Cascade simulations were performed with primary knock-on atom energies ranging between 1 and 20 KeV, hydrostatic and uniaxial strain values ranging from À2% (compression) to 2% (tensile), and temperatures ranging from 100 to 1000 K. Results demonstrated that the number of defects increased when the displacement cascade proceeded under tensile uniaxial hydrostatic strain. In contrast, compressive strain states tended to decrease the defect production rate as compared with the reference no-strain condition. The proportions of vacancy and interstitial clustering increased by approximately 45% and 55% and 25% and 32% for 2% hydrostatic and uniaxial strain systems, respectively, as compared with the unstrained system, whereas both strain fields resulted in a 15e30% decrease in vacancy and interstitial clustering under compressive conditions. Tensile strains, specifically hydrostatic strain, tended to produce larger sized vacancy and interstitial clusters, whereas compressive strain systems did not significantly affect the size of defect clusters as compared with the reference no-strain condition. The influence of the strain system on radiation damage became more significant at lower temperatures because of less annealing than in higher temperature systems.
Thermodynamic analysis of irradiation-induced amorphization of intermetallic particles in Zircaloy
Journal of Materials Science, 1995
The intermetallic precipitate particles Zr2(Ni, Fe) in Zircaloy-2 and Zr(Cr, Fe)2 in Zircaloy-4, dissolve and amorphize under irradiation. Pursuing a previous analysis by Motta and Lemaignan, we have studied those effects on the basis of the metastable free-energy diagram of the reference system Zr-Fe (calculated using Miedema's model) and considering some aspects of the modification of this free-energy diagram by irradiation. We then can explain why both phases Zr2(Ni, Fe) and Zr(Cr, Fe)2 can be amorphized at low temperatures (below 350 K) without composition changes if sufficient energy can be accumulated by irradiationproduced defects and chemical disorder, and also that at intermediate temperatures (about 580 K) a driving force exists for particle amorphization at the matrix-particle interface for Zr(Cr, Fe)2 but not for Zr(Ni, Fe)2.
Comment on 'Large swelling and percolation in irradiated zircon
Journal of Physics Condensed Matter
A recent model for the large radiation-induced swelling exhibited by irradiated zircon (ZrSiO4) is partially based on results of molecular dynamics (MD) simulations of the partial overlap of two collision cascades that predict a densified boundary of polymerized silica and the scattering of the second cascade away from the densified boundary (Trachenko et al 2003 J. Phys.: Condens. Matter 15 L1). These MD simulations are based on an atomic interaction potential for zircon (Trachenko et al 2001 J. Phys.: Condens. Matter 13 1947), which, according to our analysis, only reproduces some of the crystallographic properties at equilibrium and does not adequately describe the atomic scattering physics for zircon, and on simulation methodologies for energetic events that are ill defined. In fact, the interatomic potential model used by Trachenko et al yields a significantly more rigid structure, with very high Frenkel defect formation energies and extremely low entropy and specific heat capa...
High-energy radiation damage in zirconia: Modeling results
Zirconia is viewed as a material of exceptional resistance to amorphization by radiation damage, and consequently proposed as a candidate to immobilize nuclear waste and serve as an inert nuclear fuel matrix. Here, we perform molecular dynamics simulations of radiation damage in zirconia in the range of 0.1-0.5 MeV energies with account of electronic energy losses. We find that the lack of amorphizability co-exists with a large number of point defects and their clusters. These, importantly, are largely isolated from each other and therefore represent a dilute damage that does not result in the loss of long-range structural coherence and amorphization. We document the nature of these defects in detail, including their sizes, distribution and morphology, and discuss practical implications of using zirconia in intense radiation environments.
2012
This work is based on our reaction-diffusion model of radiation growth of Zr-based materials proposed recently in [1]. In [1], the equations for the strain rates in unloaded pure crystal under cascade damage conditions of, e.g., neutron or heavy-ion irradiation were derived as functions of dislocation densities, which include contributions from dislocation loops, and spatial distribution of their Burgers vectors. The model takes into account the intra-cascade clustering of self-interstitial atoms and their one-dimensional diffusion; explains the growth stages, including the break-away growth of pre-annealed samples; and accounts for some striking observations, such as of negative strain in prismatic direction, and co-existence of vacancy- and interstitial-type prismatic loops. In this report, the change of dislocation densities due to accumulation of sessile dislocation loops is taken into account explicitly to investigate the dose dependence of radiation growth. The dose dependence...