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Dissertations / Theses on the topic 'Crystal structure'

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Published: 4 June 2021
Last updated: 24 August 2024

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1

Schiefer, Stefan. "Crystal structure of fiber structured pentacene thin films." Diss., lmu, 2007. http://nbn-resolving.de/urn:nbn:de:bvb:19-75797.

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2

Glass, Colin William. "Computational crystal structure prediction /." Zürich : ETH, 2008. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=17852.

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3

Parker, Jane Ker. "Crystal structure reactivity correlations." Thesis, University of Cambridge, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.316782.

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4

Strehler, Frank, Marcus Korb, and Heinrich Lang. "Crystal structure of ruthenocenecarbo­nitrile." Universitätsbibliothek Chemnitz, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-166700.

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The mol­ecular structure of ruthenocenecarbo­nitrile, [Ru([eta]5-C5H4C[triple bond]N)([eta]5-C5H5)], exhibits point group symmetry m, with the mirror plane bis­ecting the mol­ecule through the C[triple bond]N substituent. The RuII atom is slightly shifted from the [eta]5-C5H4 centroid towards the C[triple bond]N substituent. In the crystal, mol­ecules are arranged in columns parallel to [100]. One-dimensional inter­molecular [pi]-[pi] inter­actions [3.363 (3) Å] between the C[triple bond]N carbon atom and one carbon of the cyclo­penta­dienyl ring of the overlaying mol­ecule are present.
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5

Saito, Junichi. "Crystal Structure of Microbial Chitosanase." 京都大学 (Kyoto University), 1999. http://hdl.handle.net/2433/181426.

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6

Conti, Elena Eliana. "Crystal structure of firefly luciferase." Thesis, Imperial College London, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.244284.

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7

Tebbutt, Iain John. "Optical activity and crystal structure." Thesis, University of Oxford, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.302911.

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8

Rowsell, Sian. "Crystal structure of carboxypeptidase G←2." Thesis, Imperial College London, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.362421.

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9

Yang, Lusann Wren. "Data Mining Chemistry and Crystal Structure." Thesis, Harvard University, 2014. http://dissertations.umi.com/gsas.harvard:11454.

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The availability of large amounts of data generated by high-throughput computing and experimentation has generated interest in the application of machine learning techniques to materials science. Machine learning of materials behavior requires the use of feature vectors that capture compositional or structural information influence a target property. We present methods for assessing the similarity of compositions, substructures, and crystal structures. Similarity measures are important for the classification and clustering of data points, allowing for the organization of data and the prediction of materials properties.
Engineering and Applied Sciences
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10

Campbell, Josh E. "Crystal structure prediction of organic semiconductors." Thesis, University of Southampton, 2017. https://eprints.soton.ac.uk/414008/.

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This thesis presents the use of crystal structure prediction (CSP) in the evaluation and design of novel organic semiconductors. Heteroatom substitution into common organic semiconductors (pentacene in this thesis) oers a way of modulating their crystal packing and electronic properties. Initially CSP was performed on six human designed molecules and the charge mobility of their predicted crystal structures was calculated. The packing landscapes changed signicantly from the unsubstituted pentacene. We found that seven nitrogen atoms led to a landscape showing a range of packing motifs, while seven nitrogen atoms favours the adoption of sheet-like motifs. Substitution patterns expected to result in the highest mobilities were found to perform worse than assumed, showing the importance of tuning both molecular electronic properties and crystal engineering. A genetic algorithm was then developed to generate new nitrogen substituted pentacenes. A population members tness was calculated using two molecular properties important for electron transport in organic semiconductors. Five runs of the genetic algorithm gave 12 promising candidates for CSP and mobility calculations. The packing landscapes were similar to those of the seven nitrogen substituted human designed molecules. One genetic algorithm molecule showed a high number of high mobility structures close to the global minimum, making this molecule an attractive target for synthesis. Extensions to include CSP within the tness function of the genetic algorithm represents possible future work. Addition work included the design and testing of structure generator for the generation of trial crystal structures during a CSP. The novel structure generator performed well in locating the experimental structures of three test molecules and was used in the group's submission to the 6th blind test, of which one molecule is also presented here. The experimental structure of this molecule was located in lists ranked by lattice energy and free energy, though the free energy list ranked the experimental structure as the global minimum.
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11

Pippel, Jan, E. Bartholomeus Kuettner, David Ulbricht, Jan Daberger, Stephan Schultz, John T. Heiker, and Norbert Sträter. "Crystal structure of cleaved vaspin (serpinA12)." De Gruyter, 2016. https://ul.qucosa.de/id/qucosa%3A33438.

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The adipokine vaspin (serpinA12) is mainly expressed in white adipose tissue and exhibits various beneficial effects on obesity-related processes. Kallikrein 7 is the only known target protease of vaspin and is inhibited by the classical serpin inhibitory mechanism involving a cleavage of the reactive center loop between P1 (M378) and P1′ (E379). Here, we present the X-ray structure of vaspin, cleaved between M378 and E379. We provide a comprehensive analysis of differences between the uncleaved and cleaved forms in the shutter, breach, and hinge regions with relation to common molecular features underlying the serpin inhibitory mode. Furthermore, we point out differences towards other serpins and provide novel data underlining the remarkable stability of vaspin. We speculate that the previously reported FKGx1Wx2x3 motif in the breach region may play a decisive role in determining the reactive center loop configuration in the native vaspin state and might contribute to the high thermostability of vaspin. Thus, this structure may provide a basis for future mutational studies.
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12

Kazantsev, Andrey. "Molecular flexibility in crystal structure prediction." Thesis, Imperial College London, 2011. http://hdl.handle.net/10044/1/9079.

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The packing of molecules in solids greatly affects the properties of the bulk materials. This is particularly important for the pharmaceutical industry, where the discovery of crystal forms at a late stage of process development can have disastrous consequences. As a result, the importance of polymorphism in crystal structures of organic molecules has been recognised for many years. This thesis presents computational developments that can complement experimental form screening of molecules for which conformational flexibility is significant. Current methods for crystal structure prediction are limited by the extent of molecular flexibility that can be practically handled due to the prohibitive computational cost associated with quantum mechanical calculations integrated in most of the successful approaches. In order to reduce the number of quantum mechanical evaluations, local approximate models can be defined for the estimation of the intramolecular energy, molecular geometry and the conformationally dependent intermolecular electrostatic model. A novel algorithm, CrystalOptimizer, for the accurate local minimisation of the lattice energy of crystals involving flexible organic molecules is presented. The main novelty of the algorithm is the use of dynamically constructed and updated local approximate models which essentially make available the full accuracy of quantum mechanical models at each and every iteration of the minimisation algorithm, requiring only a small number of explicit quantum mechanical calculations. This has made possible the accurate treatment of molecules involving a relatively large numbers of atoms with significant flexibility in torsional and bond angles and even bond lengths. The performance of the algorithm is critically assessed and demonstrated on a set of single and multi-component crystals. An extension of an existing algorithm for the identification of low energy crystal structures of flexible molecules, CrystalPredictor, is also described. In the proposed modification, the intramolecular energy and the molecular conformation are modelled using local approximate models. This provides a more realistic model for the effects of the flexible degrees of freedom on the molecular geometry and lattice energy. The use of deterministic low-discrepancy sequences ensures an extensive and uniform coverage of the multivariable search space. A parallelised implementation of the algorithm allows minimisations from several hundreds of thousands of initial guesses to be carried out in reasonable time. A further computational benefit is derived by the storage of the information used to construct the local approximate models in databases, which can be re-used in subsequent re-minimisation of structures with more accurate models for the lattice energy. The usefulness of these modifications is demonstrated on the ROY molecule, for which the structures of all experimentally known polymorphs are identified by the algorithm. By combining the above algorithms, a comprehensive multi-stage methodology for ab initio determination of the crystal structure of a given molecule based solely on its atomic connectivity is presented. The application of the methodology to two large and flexible molecules of pharmaceutical interest is also demonstrated.
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13

Farquhar, Colin Pirie. "Interface electronic structure." Thesis, University of Edinburgh, 1988. http://hdl.handle.net/1842/14824.

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14

Stevenson, Maya. "The study of structure and dynamics in organometallic compounds." Thesis, University of Oxford, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.302332.

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15

Cosquer, Guirec Yann. "Liquid crystals with novel terminal chains as ferroelectric liquid crystal hosts." Thesis, University of Hull, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.322457.

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16

Levandovsky, Artem. "Structure and dynamics of interfaces in the epitaxial growth and erosion on (110) and (100) crystal surfaces." Morgantown, W. Va. : [West Virginia University Libraries], 2004. https://etd.wvu.edu/etd/controller.jsp?moduleName=documentdata&jsp%5FetdId=3731.

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Thesis (Ph. D.)--West Virginia University, 2004.
Title from document title page. Document formatted into pages; contains vii, 129 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references.
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17

Pannu, Navraj Singh. "Improved crystal structure refinement through maximum likelihood." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp04/mq28974.pdf.

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18

Karamertzanis, Panagiotis. "Prediction of crystal structure of molecular solids." Thesis, Imperial College London, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.411320.

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19

Abraham, Nathan Luke. "A genetic algorithm for crystal structure prediction." Thesis, University of York, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.444727.

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20

Vrielink, Alice. "The crystal structure determination of cholesterol oxidase." Thesis, Imperial College London, 1989. http://hdl.handle.net/10044/1/47699.

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21

Hossain, Chintan. "The crystal structure of cholesterol helical ribbons." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/40897.

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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Physics, 2007.
Includes bibliographical references (p. 49-50).
Helical ribbons form in a many multi-component solutions containing sterols similar to cholesterol, but remarkably, almost all the helices have a pitch angle of 11⁰ or 54⁰. The consistent pitch angle of the ribbons may be due to an underlying crystal structure. In order to determine the crystal structure, I undertook x-ray scattering studies of individual helical ribbons taken from two particular solutions: Chemically Defined Lipid Solution and model bile. Using a synchrotron x-ray source I observed Bragg reflections from ribbons with a pitch angle of 11⁰. From the diffraction patterns, I was able to deduce the parameters of the unit cell. The crystal structure of these ribbons is similar to that of cholesterol monohydrate, with the important difference that the length of the unit cell perpendicular to the cholesterol layers is tripled. Furthermore, I found that adjacent layers are shifted relative to each other along a single direction, and that the shift varies periodically with a period of 3 bilayers. I also found that the growth direction of the crystal is along one of the unit cell axes.
by Chintan Hossain.
S.B.
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22

Xu, Wenjing. "Crystal structure of paired domain--DNA complex." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/32666.

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23

Mancia, Filippo. "The crystal structure of methylmalonyl-CoA mutase." Thesis, University of Cambridge, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.627037.

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24

McMahon, Malcolm Iain. "Accurate crystal structure studies at high pressure." Thesis, University of Edinburgh, 1990. http://hdl.handle.net/1842/11142.

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Diffraction techniques - incorporating both x-rays and neutrons, single-crystals and powders - have been developed to allow crystal structures to be determined at high pressures with high accuracy. For single-crystal neutron-diffraction studies, an optimised data collection strategy has been developed for use with a sapphire-anvil pressure cell and a position-sensitive detector and, combined with a newly developed clamp-type pressure cell, has allowed both the scope and accuracy of high-pressure structural studies using neutron-diffraction techniques to be extended. Application of the new techniques to high-pressure structural studies of H-ordering systems of the KH2PO4-type, strongly suggests that the H-atom site separation, δ, is a strong determinant of the ordering temperature T_c such that a hydrogenous material and its deuterated analogue have the same T_c, within error, at the same δ. The results also suggest that the differences in Tc between different H-ordering systems are determined by the differences in δ, and that δ in all systems tends to im0.22pr and Tc→OK. For single-crystal x-ray diffraction studies using a diamond-anvil cell, analysis has shown that removal of intensity from either the incident or diffracted beams by simultaneous diffraction of the diamonds can reduce the intensity of sample reflections by up to 50%. A data collection strategy to detect this effect has been developed. The use of tungsten as a gasket material has also been investigated, and provides a possible solution to the long-standing problem of using AgKα radiation for single-crystal studies. Application of these newly-developed techniques to a structural study of the high-Tc superconductor YBa2Cu4O8, illustrates the improved accuracy now available using single-crystal x-ray diffraction techniques and AgKα radiation. The results of this study cast considerable doubts on the accuracy of previous high-pressure structural studies of high-T_c superconductors. Work has also been done on developing powder-based techniques. These show considerable promise for accurate structural studies to very high pressures in the future.
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25

Lavery, Roan. "Dynamics and structure of liquid crystal colloids." Thesis, University of Edinburgh, 2001. http://hdl.handle.net/1842/11037.

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This thesis sets out to investigate the dynamic and structural properties of liquid crystal colloids. In themselves the fields of colloidal and liquid crystal science have been well studied, but the combination of these produces a wealth of new physics which has provoked much interest over the past few years. The research began by investigating the dynamics of dilute suspensions of colloidal particles in the isotropic phase of liquid crystal near the nematic transition. It was found that the particles exhibit an anomalously low diffusion which was explained in terms of the formation of an ordered layer of liquid crystal molecules surrounding the particles even when the bulk phase was disordered. It was also discovered around this time that due to the preparation procedure the particle could become coated with a thin layer of another type of solvent which dramatically affected the particle diffusion and this lead to an offshoot study in this area. It was found that the diffusion of these coated particles was much faster than expected because of a change to the boundary conditions at the particle surface as a solvent coating caused partial slip boundary conditions which altered the diffusion. Latterly the nature of this coating was investigated more and a hydrodynamic model employed to compare experimental results with the predictions given by the theory. It was found that these were in good agreement. The focus of investigation then changed, focusing on more concentrated systems of colloidal particles in liquid crystal solvents as these exhibited unusual structural phenomena. It was seen that a concentrated suspension of particles in liquid crystal shows a huge increase in the rigidity of the material in its nematic phase, compared with the pure liquid crystal. This is due to the creation of a honeycomb-like aggregate particle network, which increases the elastic strength of the material. The network formation was observed using microscopy and the elastic modulus was measured rheologically to be many orders of magnitude higher than the pure liquid crystal alone. The role of cooling rate from the isotropic to nematic phase was also investigated thoroughly as this has a large impact on the final structure of the material.
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26

Krojer, Tobias. "Crystal structure of DegP from Escherichia coli." Thesis, Cardiff University, 2004. http://orca.cf.ac.uk/55937/.

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DegP is a heat-shock protein which is localized in the periplasm of Escherichia coli. It is a common protein quality control factor and represents the only protein that can alternate between the two antagonistic activities of a protease and a chaperone in a temperature-dependent manner. In this study the crystal structure of the hexameric form of DegPs2ioA from Escherichia coli was solved at 2.8A resolution by multiple anomalous dispersion phasing. As the protein was crystallized at room temperature, this structure represents the chaperone conformation. Each DegP monomer is built up by a trypsin-like serine protease domain and two consecutive PDZ domains. The hexamer is a dimer of trimers with crystallographic D3 symmetry. Oligomerization is mediated by the protease domains and results in the formation of an internal cavity where the active sites are located. Access towards the internal cavity is controlled by the flexible PDZ domains. The protease activity is absent because access towards the active sites is blocked by the interaction of several surface loops. Furthermore, the active site geometry is distorted. The crystal structure of the wild-type DegP confirmed that the inactive conformation is not due to the artificial serine to alanine mutation of the DegPs2ioA structure but represents an inherent feature of the chaperone state to avoid unwanted proteolysis at room temperature. The crystal structure of DegP in complex with the covalent serine protease inhibitor diisopropyl fluorophosphate could not preserve the protease conformation. Analysis of degradation products by mass spectrometry revealed that the product length varies between 6 and 25 amino acid residues with a clear preference for small hydrophobic residues in the PI position. Furthermore, time-dependent analyses of degradation products by high-performance liquid chromatography showed that DegP degrades its substrates in a processive fashion, similar to other cage-forming proteases.
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27

Uzoh, O. G. "Modelling molecular flexibility for crystal structure prediction." Thesis, University College London (University of London), 2015. http://discovery.ucl.ac.uk/1460832/.

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In the crystal packing of molecules wherein a single bond links aromatic groups, a change in the torsion angle can optimise close packing of the molecule. The improved intermolecular interactions, Uinter, outweigh the conformational energy penalty, ΔEintra, to give a more stable lattice energy, Elatt = Uinter + ΔEintra. This thesis uses this lattice energy model hierarchically in a new Crystal Structure Prediction (CSP) algorithm, CrystalPredictor version 1.6, which varies the low-barrier torsion angles at the start of generating hypothetical crystal structures. The crystal structure of 1-benzyl-1H-tetrazole was successfully predicted in an informal ‘blind test’ when given the chemical diagram and the number of molecules in the asymmetric unit cell. Then, the concept of whether specific molecular fragments favour polymorphism (i.e. polymorphophore) was investigated by analysing the crystal energy landscapes of the monomorphic fenamic acid and the polymorphic derivative tolfenamic acid. The CSP results show that the polymorphophore promotes but does not guarantee polymorphism and that the substituents on the polymorphophore fragment decide the relative energies of the crystal structures. Molecular Dynamics (MD) cannot use this lattice energy model because many ab initio calculations of ΔEintra on a single molecule are expensive. However, the examination of the physical origin of the torsional barrier in fenamates aided the derivation of an analytical model fo ΔEintra. This thesis develops codes for fitting analytical intramolecular force fields to ab initio conformational profiles of fenamates. An intramolecular exp-6 atom-atom term (for the non-bonded repulsion-dispersion contributions) plus a cosine term (that represents the changes to the Molecular Orbitals) accurately model the ab initio conformational energy surfaces of fenamic and tolfenamic acids. This thesis provides a first step in extending ΔEintra data generated from CSP studies to help MD on condensed phases of pharmaceutical-like organic molecules.
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28

Bradley, K. "Crystal structure prediction for complex modular materials." Thesis, University of Liverpool, 2017. http://livrepository.liverpool.ac.uk/3005093/.

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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.
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29

Lukashev, Pavel. "Crystal and Electronic Structure of Copper Sulfides." Case Western Reserve University School of Graduate Studies / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=case1164213394.

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30

Russell, Rupert J. M. "Crystal structure of Thermoplasma acidophilum citrate synthase." Thesis, University of Bath, 1994. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.384992.

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31

Neumann, M. A., Frank J. J. Leusen, and John Kendrick. "A major advance in crystal structure prediction." Wiley, 2008. http://hdl.handle.net/10454/4740.

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no
A crystal ball? A new method for crystal structure prediction combines a tailor-made force field with a density functional theory method incorporating a van der Waals correction for dispersive interactions. In a blind test, the method predicts the correct crystal structure for all four compounds, one of which is a cocrystal. The picture shows the predicted structure of one of the compounds in green and the experimental structure in blue.
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32

Pham, Cong Huy. "Molecular crystal structure prediction with evolutionary algorithm." Doctoral thesis, SISSA, 2015. http://hdl.handle.net/20.500.11767/4884.

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The layout of the thesis is as follow: In Chapter 1, we present the theoretical background of DFT, Projector-Augmented-Wave (PAW) and Gauge-Including Projector-Augmented-Wave (GIPAW) methods. In Chapter 2, we introduce the crystal structure prediction problem and present evolutionary algorithms as one solution to perform crystal structure search for molecular crystals. Chapter 3 and Chapter 4 are dedicated to the detailed results when using evolutionary algorithm in crystal structure search for the studies of glycine and cholesterol respectively
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33

Asmadi, Aldi, M. A. Neumann, John Kendrick, P. Girard, M.-A. Perrin, and Frank J. J. Leusen. "Revisiting the Blind Tests in Crystal Structure Prediction: Accurate Energy Ranking of Molecular Crystals." American Chemical Society, 2009. http://hdl.handle.net/10454/4727.

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no
In the 2007 blind test of crystal structure prediction hosted by the Cambridge Crystallographic Data Centre (CCDC), a hybrid DFT/MM method correctly ranked each of the four experimental structures as having the lowest lattice energy of all the crystal structures predicted for each molecule. The work presented here further validates this hybrid method by optimizing the crystal structures (experimental and submitted) of the first three CCDC blind tests held in 1999, 2001, and 2004. Except for the crystal structures of compound IX, all structures were reminimized and ranked according to their lattice energies. The hybrid method computes the lattice energy of a crystal structure as the sum of the DFT total energy and a van der Waals (dispersion) energy correction. Considering all four blind tests, the crystal structure with the lowest lattice energy corresponds to the experimentally observed structure for 12 out of 14 molecules. Moreover, good geometrical agreement is observed between the structures determined by the hybrid method and those measured experimentally. In comparison with the correct submissions made by the blind test participants, all hybrid optimized crystal structures (apart from compound II) have the smallest calculated root mean squared deviations from the experimentally observed structures. It is predicted that a new polymorph of compound V exists under pressure.
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34

Saito, Kaichi. "Real crystal structure related to superconductor properties of YBa₂Cu₃O₇₋{delta} single crystals /." Zürich, 1997. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=12105.

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35

Thompson, Hugh Patrick George. "Extending crystal structure prediction methods towards flexible molecules." Thesis, University of Cambridge, 2015. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.708949.

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36

Forsyth, G. A. "Molecular structure by diffraction methods." Thesis, University of Reading, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.384586.

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37

Nielsen, Tine Kragh. "Crystal structure of a human U5 snRNP specific binary complex and crystal structure of a histone deacetylase-like bacterial amidohydrolase." Doctoral thesis, [S.l.] : [s.n.], 2005. http://webdoc.sub.gwdg.de/diss/2005/nielsen.

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38

Hoang, Quyen Quoc Yang Daniel. "Crystal structure and hydroxyapatite binding of porcine osteocalcin /." *McMaster only, 2003.

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39

Fukami, Takaaki. "Crystal Structure of Chaperonin-60 from Paracoccus denitrificans." 京都大学 (Kyoto University), 2001. http://hdl.handle.net/2433/150394.

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40

Narine, Suresh S. "Structure and mechanical properities of fat crystal networks." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape2/PQDD_0023/NQ51043.pdf.

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41

Zuccola, Harmon Jay. "The crystal structure of monoferric human serum transferrin." Diss., Georgia Institute of Technology, 1992. http://hdl.handle.net/1853/26304.

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42

Cooper, Richard Ian. "A semi-expert system for crystal structure analysis." Thesis, University of Oxford, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.342216.

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43

Booyens, Sharon. "Structure and reactivity of iron single crystal surfaces." Thesis, Cardiff University, 2010. http://orca.cf.ac.uk/54195/.

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Measurements with a molecular beam reactor show that the initial sticking probability of C2H4 on Fe(111) decreases with temperature from 0.35 at 373 K to 0.13 at 873 K. Steady state sticking commences above 573 K and only steady state sticking is observed above 723 K. Between 373 and 673 K the carbon deposits resulting from C2H4 dosing decrease O2 sticking compared to the clean surface, since the surface now accommodates both species. Above this temperature O2 sticking increase significantly compared to the clean surface as it reacts with surface C to form CO gas. Clean off experiments suggest that surface oxygen provides a driving force for C in the subsurface/bulk to segregate to the surface.
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44

Troughton, Michael John. "The structure and properties of liquid crystal polymers." Thesis, University of Leeds, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.383929.

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45

Prasetya, Fajar. "Crystal structure of Pseudomonas aeruginosa condensing enzyme PqsBC." Thesis, University of Nottingham, 2018. http://eprints.nottingham.ac.uk/55456/.

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Pseudomonas aeruginosa is an opportunistic bacterium that can infect immunocompromised people, and is especially prevalent in patients with cystic fibrosis. Treatment of P. aeruginosa is complicated due to resistance to many classes of antibiotics. This is partly due to biofilm formation, which is not simply a diffusion barrier, but also has a distinct mechanism for resisting the action of antibiotics. P. aeruginosa quinolone signal (PQS) has an important role in quorum sensing, which is involved in biofilm formation. PqsBC is a condensing enzyme in the biosynthesis of the PQS. The crystal structures of PqsBCC129A and PqsBCC129A-Fe3+ were collected to 2.04 Å and to 2.3 Å, respectively. The crystal structure showed that PqsB and PqsC have a pseudo 2-fold symmetry that mimics the FabH homodimer as well as the presence of a catalytic diad instead of the typical catalytic triad in PqsBC, seen in other FabH family enzymes. The PqsCC129A active site volume is twice the volume as those of FabH enzymes or PqsD, with a calculated volume of 761Å3, compared to 389Å3 for PqsD and 367Å3 for FabH.The PqsBCC129A-Fe3+ crystal structure shows that Fe3+ binds to nitrogen atoms from PqsB His282 and PqsC His2 along with oxygen atoms from PqsB Glu48 and Glu280. Therefore, there are four bonds involved in the interaction between Fe3+ and PqsBCC129A. These bond lengths are very similar to those observed in the structures of Azurin and FutA1 complexed with iron. These crystal structures of PqsBC provide a unique insight into substrate recognition and establish a scaffold for structure guided drug design of novel antimicrobial agents.
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46

Fischer, Christopher Carl. "A machine learning approach to crystal structure prediction." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/42132.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2007.
Includes bibliographical references (p. 137-147).
This thesis develops a machine learning framework for predicting crystal structure and applies it to binary metallic alloys. As computational materials science turns a promising eye towards design, routine encounters with chemistries and compositions lacking experimental information will demand a practical solution to structure prediction. We review the ingredients needed to solve this problem and focus on structure search. This thesis develops and argues for a search strategy utilizing a combination of machine learning and modern quantum mechanical methods. Structure correlations in a binary alloy database are extracted using probabilistic graphical models. Specific correlations are shown to reflect well-known structure stabilizing mechanisms. Two probabilistic models are investigated to represent correlation: an undirected graphical model known as a cumulant expansion, and a mixture model. The cumulant expansion is used to efficiently guide Density Functional Theory predictions of compounds in the Ag-Mg, Au-Zr, and Li-Pt alloy systems. Cross-validated predictions of compounds present in 1335 binary alloys are used to demonstrate predictive ability over a wide range of chemistries - providing both efficiency and confidence to the search problem. Inconsistencies present in the cumulant expansion are analyzed, and a formal correction is developed. Finally, a probabilistic mixture model is investigated as a means to represent correlation in a compact way. The mixture model leads to a significant reduction in model complexity while maintaining a level of prediction performance comparable to the cumulant expansion. Further analysis of the mixture model is performed in the context of classification. Unsupervised learning of alloy classes or groups is shown to reflect clear chemical trends.
by Christopher Carl Fischer.
Ph.D.
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47

Allan, David Robert. "Crystal-structure studies and techniques at high pressure." Thesis, University of Edinburgh, 1993. http://hdl.handle.net/1842/17021.

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This thesis is concerned with the application of high-pressure diffraction techniques - involving both x-rays and neutrons, single crystal and powder samples - to the study of crystal-structures at high pressure and to the development of such techniques for the determination of crystal-structures with greater accuracy and more reliability. The current state-of-the-art high-pressure diffraction techniques are reviewed and applied to the study of a number of interesting materials. The crystal structure of KTiOPO4(KTP) has been determined as a function of pressure as its phase transition at 5.5 GPa is approached, using single-crystal x-ray diffraction techniques. The principal changes with pressure are in the co-ordination environments of the potassium atoms and in the linking angles of the TiO6-PO4 structural framework. In general the distortions of the TiO6 octahedra, which have been linked to the second harmonic generating properties of KTP, are retained although there are some small changes in the Ti-O bond lengths. The structure of the high-pressure phase of KTP has also been determined, using single-crystal x-ray diffraction, and it appears that, although the phase transition is strongly first-order and involves a 4.2% reduction of the unit-cell volume, the Pna21 space-group symmetry of the low-pressure phase is retained. The main structural changes at the phase transition involve tilting of the PO4 tetrahedra relative to the TiO6 octahedra, while both units remain relatively unchanged in size and shape. In particular, the TiO6 octahedra remain highly distorted and retain their anomalously short Ti-OT bonds. The potassium atoms are also observed to undergo relatively large movements of about 0.5 AA along the polar c-axis at the transition. The crystal structure of KH2PO4 (KDP) has been determined at 2.9 GPa, a pressure just below that of its high-pressure ambient-temperature phase transition, using single-crystal neutron diffraction. It appears that the oxygen-oxygen distance, 2R, undergoes a uniform compression to 2.9 GPa which is moderated by the rotation of the essentially rigid PO4 tetrahedra around their =4-axes.
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48

Chaka, Anne Marie. "Predicting the crystal structure of organic molecular materials." Case Western Reserve University School of Graduate Studies / OhioLINK, 1993. http://rave.ohiolink.edu/etdc/view?acc_num=case1056642240.

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49

Kwofie, Samuel Kojo. "The crystal structure of a mutant nitrile hydratase." Master's thesis, University of Cape Town, 2006. http://hdl.handle.net/11427/4284.

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Includes bibliographical references.
Nitrile hydratases can be used as industrial biocatalysts. They catalyze the conversion of nitriles to their corresponding amides. These industrial biocatalysts have recently gained attention due to the economic production of industrial commodities such as acrylamide and nicotinamide (Thomas et at., 2002). Nitrile hydratases (NHases) are metalloenzymes made up of α and β subunits, and exist mostly as heterotetramers (αβ)₂. They are categorized into Co-containing and Fe-containing types depending on their co-factor requirements.
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50

Baca, Arthur Martin. "Crystal structure of dihydropteroate synthase from Mycobacterium tuberculosis /." Thesis, Connect to this title online; UW restricted, 2000. http://hdl.handle.net/1773/8079.

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