Prediction and characterisation of radiation damage in fluorapatite

Abstract

Molecular dynamics simulations, used in conjunction with a set of classical pair potentials, have been employed to examine simulated radiation damage cascades in the fluorapatite structure. Regions of damage have subsequently been assessed for their ability to recover and the effect that damage has on the important structural units defining the crystal structure, namely phosphate tetrahedra and calcium meta-prisms. Damage was considered by identifying how the phosphorous coordination environment changed during a collision cascade. This showed that PO 4 units are substantially retained, with only a very small number of under or over coordinated phosphate units being observed, even at peak radiation damage. By comparison the damaged region of the material showed a marked change in the topology of the phosphate polyhedra, which polymerised to form chains up to seven units in length. Significantly, the fluorine channels characteristic of the fluorapatite structure and defined by the structure's calcium meta-prisms stayed almost entirely intact throughout. This meant that the damaged region could be characterised as amorphous phosphate chains interlaced with regular features of the original undamaged apatite structure.

Exploring the Thermodynamic Behavior and the Effect of Temperature and Electron Radiation on the Structure of Fluorapatite Compounds

“…Similar effect was predicted by Jay et.al. from molecular dynamics study of fluorapatite by alpha radiation cascade [43] . As predicted by their study a large proportion of PO 4 3− group are remained intact however within the core of the damaged region, small amount of PO x units is found to get stabilized in chain like P−O−P structure.…”

In situ TEM observation of alpha-particle induced annealing of radiation damage in Durango apatite

“…Thus, the grains are considered to be amorphous when all the diffraction spots disappear after Kr ion irradiations. However, because of the recrystallization along exactly the same orientation, it is likely that there is a glass-like material where the aperiodic rotations of phosphate tetrahedra are sufficient to distort the atoms and cause the disappearance of diffraction spots after Kr ion damage, while the fluorine channels of the fluorapatite structure remained almost intact, as discovered by the Molecular Dynamics (MD) simulation 36 . The undamaged fluorine channels 36 after Kr ion irradiation may provide a framework for the recovery of the structure in the same orientation by the irradiation of alpha-particles.…”

“…However, more recent work reported much higher values, ~5,000 for alpha-recoil in natural zircon 46 and 10,000 for 239 Pu in a PuCoGa 5 superconductor 47 , using Nuclear Magnetic Resonance (NMR) and Extended X-Ray Absorption Fine Structure (EXAFS), respectively. The MD simulation gives a final ~2,000 displaced atoms per 5 keV recoil in apatite 36 . In order to compare 70 keV Th damage in natural apatite and 1 MeV Kr ion irradiations, SRIM simulation is used in both cases for consistency.…”

Effects of Ag+ Ion Doping on UV Radiation Absorption and Luminescence Profiles of Fluorapatite Nanomaterials Obtained by Neutralization Method

“…Ca 10 (PO 4 ) 6 F 2 (FAP) nanocrystals have been playing important role in the development of suitable luminescent materials for ionizing and non-ionizing radiation dosimetry, and protection as well [1][2][3][4]. In last few decades, UV radiation measurements and protection attracted high attention considering the harmful effects on ecosystems as a consequence of degradation of ozone layer, but also the biological effects of high energy photons of the UV radiation on eyes and skin [5,6].…”