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Title: Application of atomistic modelling to molecular solids containing hydrogen bonds
Author: Maarof, Hasmerya
ISNI:       0000 0004 2748 5765
Awarding Body: Cardiff University
Current Institution: Cardiff University
Date of Award: 2009
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The work presented in this thesis is mainly concerned with crystal structures containing hydrogen bonds. Chapter 1 and 2 mainly discuss the background and basic concepts used in this study such as the importance of hydrogen bond in crystal engineering, co-crystals and polymorphism, and recent studies of urea co-crystals. Chapter 3 is a study about urea/oc,co-dihydroxyalkanes co-crystal structures. It begins with parameterising DMAREL to obtain lattice energy from a set of homologous co- crystals where DMA multipoles were generated from different method, GDMA and MOLPRO. The simulated lattice energy, structures and interaction energy were discussed and compared whether there is possibilities for the co-crystals to appear in different urea ribbon structures (parallel and anti-parallel) as these could not be crystallised experimentally. The energy data shows that urea/a,co-dihydroxyalkanes co-crystal of anti-parallel ribbon type structure are more thermodynamically favoured compared to the parallel structure. In latter part of this chapter, attempts to construct and simulate the anti-parallel urea ribbon co-crystal type structures from initial experimental structures were discussed. In Chapter 4, sulfur pair potential was modelled to fit for use in DMAREL for TTCA structure simulation. The original potentials were taken from Lennard Jones potential of a-S8 crystal structure. Initially, the potentials were modelled against a-Sg and thiourea crystal. Improved potentials were applied to a set of S-contained structure, specifically with similar environment to TTCA to validate the reliability of this potential against other molecules. Potentials works fairly well for 5 out of 10 molecules simulated, where TTCA shows poorest performance against the potential even though it has improved from the original sulfur potential. Contrasting crystal structure between TTCA and CA when substituted between each other is discussed. The final chapter, Chapter 5 is the continuation from work in Chapter 3. In urea co-crystal, it was found that urea structure was not exactly planar. We then continue on the search of different conformation of urea molecule in as and solid structure. First, the conformation of urea monomer were discussed and followed by calculation of larger planar urea clusters where one of the urea is substituted with either Cj or Cs conformers. Urea clusters were build systematically mimicking dense urea crystal structure. Planar structure was finally obtained by using 5 urea molecules involving four hydrogen bonds.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available