Crystal Structure Prediction for Complex Modular Materials

Bradley, K (2017) Crystal Structure Prediction for Complex Modular Materials. PhD thesis, University of Liverpool.

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Abstract

This thesis concerns work on the structure solution and prediction of novel inorganic compounds, with specific focus on compounds that show potential use in commercial applications. The ability to predict structures at the atomic and molecular scale is a challenge at the forefront of inorganic and materials chemistry. Complex functional transition metal oxides can generally be described in terms of modules containing elements in particular chemical environments. This observation has led to the development of the Extended Module Materials Assembly (EMMA) approach for the generation of plausible candidate structures. The EMMA method is extended in this project to examine hexagonal perovskites and is first applied to Ba(Co,Nb)1-dO3, examining known structures to facilitate the discovery of new structures within the structural series. In the second instance, the EMMA method is applied to Ba3Nb2O8, which has an unconfirmed structure experimentally. It is in this case that the advantages and disadvantages of the EMMA method become increasingly apparent, with structures identified in the initial screening using classical lattice dynamics becoming less stable when re-ranked with density functional theory. Moving away from the EMMA method, a mixed system of LiMgPO4 and Li2MgSiO4 is investigated based on Monte Carlo site-swapping in an ideal oxide lattice. As with the EMMA approach, this method has several advantages and disadvantages, with successes seen for some compositions but not in others. The results in this thesis demonstrate the difficulty in rising to the challenge of crystal structure prediction and the exciting avenues that can be explored to help find answers. It is hoped that the work in this thesis can be built on in the future, through optimisation of the above methodologies and experimental synthesis of predicted compounds.

Item Type:	Thesis (PhD)
Divisions:	Faculty of Science and Engineering > School of Physical Sciences
Depositing User:	Symplectic Admin
Date Deposited:	17 Aug 2017 13:55
Last Modified:	19 Jan 2023 07:20
DOI:	10.17638/03005093
Supervisors:	Darling, G
URI:	https://livrepository.liverpool.ac.uk/id/eprint/3005093