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Trinity College Dublin

Ongoing Research Projects supported by TCHPC

TCHPC allocates resources to assist research in many different fields. Below is a list of current projects been undertaken with the help of TCHPC.
  • Chemistry
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    Prof. Graeme Watson
    Trinity College Dublin
    TiO2 has long been examined as a potential material for photochemical activity with applications in dye sensitized solar cells, photocatalytic degradation of environmental pollutants and water splitting for H2 generation.The main issue with TiO2 has been the adsorption of visible light as TiO2 has a band gap of > 3eV making it transparent. There has been interest in attempting to dope TiO2 to reduce its band gap but many of these attempts have been unsuccessful.Of particular interest is recent attempts to dope Rutile TiO2 (e.g. with Sn) as most studies have concentrated on the anatase phase of TiO2 which normally displays greater photochemical activity.\n
  • Chemistry
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    Dr Mauro Ferreira
    Trinity College Dublin
    This project investigates the properties of graphene - a novel material receiving much attention in the literature due to a wealth of unique and technologically applicable properties.Our work focuses on the properties of graphene and related materials in the presence of disorder.This can be in the form of vacancy defects or impurity atoms and can arise through deliberate introduction or through the limits of the manufacture process.Of particular interest is the effect of disorder on the potential application of graphene to spintronics.Graphene-based materials have been suggested as a waveguide for spin current - mediating the transport of information in a spintronics device - due to the long spin diffusion length and low spin-orbit coupling in this material.However, disorder in nanoribbons, 1D strips of graphene, is known to induce significantly larger bandgaps in these materials than predicted for the pristine case due to the onset of localisation phenomena.Using a Greens function formalism, we investigate how the spin current is effected in such a disordered graphene system.\n
  • Physics
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    Dr Stefan Hutzler
    Trinity College Dublin
    We probe the relationship between dynamics on the bubble scale and bulk foam rheology, using Soft Disk Model simulations. We observe two distinct regimes, classified by the nature of the bubble motion. The first regime is well-described by the Herschel-Bulkley equation, finding a value for the power law exponent, linking excess-stress to strain rate in line with previous results using the Soft Disk Model. We observe the bubbles moving in strongly non-affine, swirl-like motions. Examining the non-affine mean square displacements of the bubbles, we seek to probe the clear transition to shear-induced diffusion over a sufficiently large time interval. We aim to fit diffusion constants as functions of strain rate. We extract a characteristic relaxation time and use it to fit a relaxation model to the shear stresses measured, comparing it with the measured stresses and the Herschel-Bulkley fit.In the second regime, we observe the bubbles to begin to move in lanes. The measured stresses can no longer be fit by the Herschel-Bulkley equation, instead appearing to tend towards a linear relationship with strain rate at very high strain rate, consistent with proposed theories. We seek to further investigate the causes of this transition to lamellar flow.
  • Life Sciences
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    Dr. Trevor Hodkinson
    Trinity College Dublin
    University of Lausanne, Switzerland
    Grasses have received considerable attention as a source of woody biomass for bioenergy production to provide alternatives to fossil fuels. Potential bioenergy grasses include Miscanthus, maize, switchgrass and several woody bamboos. Most grasses are herbaceous but some subfamilies have evolved woodiness. Bamboos (subfamily Bambusoideae) have evolved a woody character via enhancement of the lignocellulosic component of vascular tissue, especially vessels. Reeds (e.g. Arundo, Phragmites, subfamily Arundinoideae) and Panicoideae (e.g. Saccharum, Miscanthus, Panicum) have also evolved this trait. It is not known if they have achieved this via alternative biosynthetic paths/genes. Grass cell walls differ from other angiosperms in their major structural polysaccharides, pectins, proteins and phenolic compounds. Recent advances in genomics have revealed cellulose synthase‐like (Csl) gene families (unique to grasses) and the CslF gene (unique to Poales, the order to which the grass family belongs). An understanding of how these gene families and lignocellulosic biosynthesis evolved in grasses is key to improving the processing quality of grasses for bioenergy and the manipulation of the genes in future biotechnology and plant breeding. Objectives and methodology: 1) Investigate, via a candidate gene approach, the evolution of genes known to be of importance for woodiness in grasses (e.g. cellulose synthase genes, Cesl, a highly expressed gene family in developing vascular fibres, including CslF, and monolignol biosynthesis genes. 2) Investigate the effects of woodiness on grass evolution (e.g. investigate, using diversification statistics and molecular dating, whether woodiness was a significant key innovation for speciation in the groups that have evolved it).
  • Chemistry
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    Dr Isabel Rozas
    Trinity College Dublin
    A family of potential alpha 2 adrenoceptor antagonists was previously identified and, in particular, the conformational preferences of these molecules was investigated using the Gaussian program. The molecules were subsequently synthesised and biologically tested. The promising biological results showed definite patterns, the reasons for which could be explained by further computational analysis of the molecules\' properties. This work will aid in the design of future ligands for the alpha 2 adrenoceptor leading to the real possibility of finding a new class of antidepressant with improved efficacy and reduced side effects.
  • Chemistry
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    Prof. Graeme Watson
    Trinity College Dublin
    P. R. L. Keating, D. O. Scanlon, B. J. Morgan, N. Galea and G. W. WatsonCeO2 (ceria) has emerged in recent years as an important material for a wide variety of applications. CeO2 can be found in many catalytic processes, most notably in the catalytic converters of cars, both as a support and an active catalyst. CeO2 is also a promising candidate for the electrolyte material in solid oxide fuel cells, a highly efficient and environmentally friendly form of energy production. There is even evidence of intrinsic ferromagnetism in nano-sized CeO2 suggesting possible applications as a dilute magnetic semiconductor. Despite an abundance of research on the properties of CeO2, a full study of its native defects does not currently exist in the literature. We shall investigate the formation of intrinsic defects within CeO2 using density functional (DFT) theory with on-site Coulomb correction (DFT U). The ability of DFT U to correctly model the electronic structure of certain defects in CeO2, such as localized electrons from the formation of oxygen vacancies, has been well documented in the past, but other defect states involving holes produced by p-type defects have not received the same attention. We shall demonstrate that the calculations of intrinsic defects in CeO2 can be improved by introducing two U parameters, one on Ce4f states and another on O2p states. By employing an ab initio fitting procedure we hope to determine a value of U{O2p} that reproduces the localized nature of the p-type defect states. We carry out chemical potential and temperature dependence analyses to find the formation energies of the intrinsic defects and their relative abundance in CeO2.
  • Chemistry
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    Prof. Graeme Watson
    Trinity College Dublin
    P. R. L. Keating, D. O. Scanlon and G. W. WatsonCeO2 has been shown to be a promising candidate for the electrolye in intermediate temperature solid oxide fuel cells. Stoichiometric CeO2 is a poor ionic conductor, displaying a conductivity of around 3.13x10-3 Scm-1. Furthermore, at low oxygen pressures CeO2 displays unwanted electronic conductivity which can short circuit the fuel cell. However, the ionic conductivity of CeO2 can be greatly increased through the introduction of dopants. The most common candidates for doping CeO2 are trivalent cations such yttrium, lanthanum, gadolinium and bismuth. These dopants form charge compensating oxygen vacancies which can act as potential pathways for ionic diffusion. The advantage of oxygen vacancies formed in this way is that they do no introduce the unwanted electronic conductivity associated with reduced CeO2. We are currently investigating CeO2 doped with a series of trivalent cations using DFT U techniques. Our goal is to determine suitable dopants that will increase the ionic conductivity while hindering further reduction of CeO2. Ultimately we hope to predict suitable materials for the next generation of solid oxide fuel cells.
  • Mathematics
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    Prof. Simon Wilson
    Trinity College Dublin
    Bayesian inference for phase-type distributions is considered when data consist only of absorption times. Extensions to the methodology developed by Bladt et al. (2003) are presented which enable specific structure to be imposed on the underlying continuous time Markov process and expand computational tractability to a wider class of situations.The conditions for maintaining conjugacy when structure is imposed are developed. Part of the original algorithm involves simulation of the unobserved Markov process and the main contribution is resolution of computational issues which can arise here.The extended methodology thus improves modelling and tractability of Bayesian inference for phase-type distributions where there is direct scientific interest in the underlying stochastic process: the added structural constraints more accurately represent a physical process and the computational changes make the technique practical to implement. A simple application to a repairable redundant electronic system when ultimate system failure (as opposed to individual component failure) comprise the data is presented. This provides one example of a class of problems for which the extended methodology improves both parameter estimates and computational speed.
  • Chemistry
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    Prof. Graeme Watson
    Trinity College Dublin
    Solid oxide fuel cells (SOFCs) are devices which generate electricity from a variety of sources, such as hydrogen or hydrocarbons. This electrolytic conversion can reach efficiencies of up to 85%. Current electrolyte technology used in solid oxide fuel cells requires high operational temperatures which makes them expensive to build and impractical in all but very large scale facilities. Our goal is therefore the study of conductivity in yttrium-doped ceria (Ce1-xYxO2-x/2,)which can be used at intermediate temperature regimes. In this project we seek to rationalize the effect of aliovalent doping on the conductivity of CeO2 using atomistic and ab initio modelling methods, the results of which will be compared with experimental data gathered by Dr Stephen Hull’s group at ISIS in the UK. We have developed an interatomic potential for yttrium-dopedceria from DFT calculations, in collaboration with Prof Paul Madden’s group in Oxford.This potential, which allows for the description of dipole polarizabilites in the species being simulated, will then used in molecular dynamics simulations that can be run for time periods in the nano second scale; this is a clear advantage over full ab initio simulations of the systems in question, which using current hardware make simulations beyond 10ps impractical. Our calculations will allow the determination of properties including ionic conductivity, vacancy formation energies, residence times and structural data, such as the radial distribution function,which are key to our understanding of materials for the next generation of SOFCs.
  • Physics
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    Prof. Stefano Sanvito
    Trinity College Dublin
    The project is divided in two parts. First, we aim at investigating the physics of strongly correlated electronic systems. We have developed an Auxiliary Field Quantum Monte Carlo code which allows us to solve numerically many models relevant to describe the main features of several materials including superconductors, diluted magnetic semiconductors, Mott insulators etc.... Second, we aim at studying the electronic structure of small transition metal complexes through Diffusion Monte Carlo simulations, performed using the Casino code. Unfortunately, for such molecules, 'standard' electronic structure techniques (Density Functional Theory and Hartree-Fock) fail in predicting the correct magnetic ground state and more accurate and computationally expensive quantum chemistry methods are required. Our results will provide new insights into the physics and chemistry of these systems.

Last updated 08 Jul 2014Contact TCHPC: info | support.