@phdthesis{discovery10188848,
           title = {Stacking Disorder as a Critical Tuning Parameter for the
Properties of Materials},
            year = {2024},
           month = {March},
            note = {Copyright {\copyright} The Author 2023. Original content in this thesis is licensed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) Licence (https://creativecommons.org/licenses/by-nc/4.0/).  Any third-party copyright material present remains the property of its respective owner(s) and is licensed under its existing terms.  Access may initially be restricted at the author's request.},
          school = {UCL (University College London)},
          author = {Smith, Rachael Louise},
        abstract = {Stacking disorder is a complex yet vital phenomenon that in principle, can occur in every
layered material.1-9 The need for a thorough understanding of stacking disorder has only
become apparent within the last 12 years, 10 together with the extensive impact this has
on material properties. This thesis builds upon stacking disorder research explored
previously for diamond 2, 7, 11, 12 in addition to new studies on AgI, CuI, AgI-CuI, and
provides insight into the theoretical aspects of stacking disorder and third-order memory
effects.
This thesis focuses initially on stacking disorder in AgI, where it has been found
that the dependence of the Ag+ and I- ratios allows for targeted precipitation of cubicities
in the 0-81\% range. AgI samples exhibiting varying polarity, originating from preparation
method, have been shown to experience surface ion adsorption effects with cations. A link
between AgI cubicity and associated band gap energies has also been found. In addition,
when heating AgI to the high temperature {\ensuremath{\alpha}}-phase, samples exhibited memory effects,
and this is hypothesised to relate to the surface stabilisation by ions.
CuI did not exhibit any stacking disorder, however this research has given greater
insight into the characteristics of this material. Stacking disorder in AgI-CuI was explored
by adjusting the starting ratios of ions, showing a tendency of the resultant material to
form cubic polytypes amongst potential new phases and stacking disordered structures
when a deficiency of I- was exploited.
Investigations into Popigai diamond samples showed hexagonalities of 0-39\%.
Additional peaks in XRD patterns at 2{\ensuremath{\theta}}=12 o in combination with DIFFaX simulations
and HRTEM suggested the presence of extended graphitic regions resulting in both type
1 and 2 diaphite.
The final chapter focuses on evolving theoretical aspects of stacking disorder,
developing MCDIFFaX to incorporate third-order stacking probabilities and fitting of
high-order memory effect simulations.},
             url = {https://discovery.ucl.ac.uk/id/eprint/10188848/}
}