Pressure-induced structural transformations in nanomaterials : towards high accuracy large length- and time-scale simulations
The study of pressure-induced structural transformations in nanomaterials is both of fundamental and technological importance. Accurate simulations of these transformations are challenging because large length- and time-scales have to be simulated to make contact with experiments whilst retaining th...
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ndltd-bl.uk-oai-ethos.bl.uk-6955212018-04-04T03:22:28ZPressure-induced structural transformations in nanomaterials : towards high accuracy large length- and time-scale simulationsCorsini, NiccoloHaynes, Peter2015The study of pressure-induced structural transformations in nanomaterials is both of fundamental and technological importance. Accurate simulations of these transformations are challenging because large length- and time-scales have to be simulated to make contact with experiments whilst retaining the atomic detail for a faithful description. In this thesis, both classical and quantum mechanical techniques are used to model pressure-induced structural transformations in realistic Si, Ge and CdS nanocrystals and comparison made to experiment where possible. We implement an electronic enthalpy method within the linear-scaling density-functional theory ONETEP code and, after introducing an approach for calibrating the volume definition, investigate the size-dependent pressure-induced amorphisation and polyamorphic transformations in hydrogenated Si and Ge nanocrystals. For the latter, we elucidate the surface-induced amorphisation and the new high-density amorphous metallic Ge phase observed experimentally. We combine this method with the projector-augmented wave and time-dependent density-functional theory methods to study the size and ligand dependence of deformation and optoelectronic properties of CdS nanocrystals with pressure. We develop a novel classical parametrisation for the simulation of bare and ligated CdS nanocrystals immersed in a pressure-transmitting medium and investigate their transformation under pressure using classical molecular dynamics and the metadynamics method for accelerating rare events. The resulting polymorphic transformation and pressure-induced amorphisation are analysed in detail.620Imperial College Londonhttp://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.695521http://hdl.handle.net/10044/1/42247Electronic Thesis or Dissertation |
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620 Corsini, Niccolo Pressure-induced structural transformations in nanomaterials : towards high accuracy large length- and time-scale simulations |
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The study of pressure-induced structural transformations in nanomaterials is both of fundamental and technological importance. Accurate simulations of these transformations are challenging because large length- and time-scales have to be simulated to make contact with experiments whilst retaining the atomic detail for a faithful description. In this thesis, both classical and quantum mechanical techniques are used to model pressure-induced structural transformations in realistic Si, Ge and CdS nanocrystals and comparison made to experiment where possible. We implement an electronic enthalpy method within the linear-scaling density-functional theory ONETEP code and, after introducing an approach for calibrating the volume definition, investigate the size-dependent pressure-induced amorphisation and polyamorphic transformations in hydrogenated Si and Ge nanocrystals. For the latter, we elucidate the surface-induced amorphisation and the new high-density amorphous metallic Ge phase observed experimentally. We combine this method with the projector-augmented wave and time-dependent density-functional theory methods to study the size and ligand dependence of deformation and optoelectronic properties of CdS nanocrystals with pressure. We develop a novel classical parametrisation for the simulation of bare and ligated CdS nanocrystals immersed in a pressure-transmitting medium and investigate their transformation under pressure using classical molecular dynamics and the metadynamics method for accelerating rare events. The resulting polymorphic transformation and pressure-induced amorphisation are analysed in detail. |
author2 |
Haynes, Peter |
author_facet |
Haynes, Peter Corsini, Niccolo |
author |
Corsini, Niccolo |
author_sort |
Corsini, Niccolo |
title |
Pressure-induced structural transformations in nanomaterials : towards high accuracy large length- and time-scale simulations |
title_short |
Pressure-induced structural transformations in nanomaterials : towards high accuracy large length- and time-scale simulations |
title_full |
Pressure-induced structural transformations in nanomaterials : towards high accuracy large length- and time-scale simulations |
title_fullStr |
Pressure-induced structural transformations in nanomaterials : towards high accuracy large length- and time-scale simulations |
title_full_unstemmed |
Pressure-induced structural transformations in nanomaterials : towards high accuracy large length- and time-scale simulations |
title_sort |
pressure-induced structural transformations in nanomaterials : towards high accuracy large length- and time-scale simulations |
publisher |
Imperial College London |
publishDate |
2015 |
url |
http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.695521 |
work_keys_str_mv |
AT corsininiccolo pressureinducedstructuraltransformationsinnanomaterialstowardshighaccuracylargelengthandtimescalesimulations |
_version_ |
1718618755712417792 |