Radiation damage in xenotime: an atomistic modelling and x-ray total scattering study

Cutts, Geoffrey (2017). Radiation damage in xenotime: an atomistic modelling and x-ray total scattering study. University of Birmingham. Ph.D.

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Abstract

This thesis focuses on understanding radiation da mage processes du e to a-decay events in xenotime (YPO.). Novel atomistic potentials were derived using a reverse Monte Carlo fitting routine. These potentials were validated using morphological predictions , showing good agreement with natural samples. Intrinsic defects were modelled and binding energies were calculated to investigate their clustering behaviour. Solution energies were calculated for the substitution of lanthanide elements into the lattice, which were found to b e relatively unfavourable. Molecular dynamics simulations were utilised to model damage cascades within xenotime and zircon.
Clear differences were observed in the distributions of defects and the polymerised tetrahedral units, which may contribute the improved radiation resistance of xenotime over zircon. Threshold displacement energies were calculated for xenotime utilising the Fibonacci lattice. These showed good agreement with literature sources and may be of use in future experimental studies. Finally swift heavy ion irradiated samples of xenotime were investigated using the X-ray pair distribution function (PDF). A fission track simulation was performed to help inform the experiment, however the damage could not be characterized. The ordering of strontium atoms in mixed fluorapatite samples were also investigate using X-ray PDF, however alterative modelling techniques may be required to analyse this data.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):