MESAS research has been in the media recently from ABC Australia to CNN and Sky News.
Please see both the Sheffield University press release and the Warwick University press release for details along with the paper itself: Structural Control of Crystal Nuclei by an Eggshell Protein.
A selection of the news stories:
I should add that plenty of these articles were constructed without consultation with either myself or the rest of the research team at Sheffield or Warwick. Particularly plenty of the quotes are not necessarily real quotes!
Spreading the load: Parallel Quantum Dynamics Calculations
Dr Anthony JHM Meijer
Department of Chemistry, University of Sheffield
Tea, coffee and cakes in the Turner Museum from 2.30 Hadfield Building
30 Jun 2010 - 15:00
LT22, Hadfield Building
A talk given by Dr Anthony JHM Meijer from the Department of Chemistry, University of Sheffield
Tea, coffee and cakes in the Turner Museum will be available from from 2.30 pm in the Hadfield Building
Tea, coffee and cakes in the Turner Museum from 2.30pm
Structural Diversity in Sterically Frustrated Liquid Crystals
Professor Goran Ungar
Department of Engineering Materials, University of Sheffield
A wide range of complex thermotropic structures with 2d and 3d periodicitiy can be generated by mesogens of awkward shape, including wedge, cone, X- and T-shape. Examples will be shown of how packing frustration and conflicts between steric effects and weak interactions can lead to large unit cells from small molecules, superlattices, helical structures, hollow tubes and spheres, quasicrystals, as well as unusual phase transitions.
Formation of Zeo-Morphic Structures in Template Hydration
Dr Keith Butler
Department of Engineering Materials, University of Sheffield, formally at University College London
Structure-directing agents (SDAs) are often included in the synthesis of zeolite
crystals in order to obtain a specific crystal structure, the exact role of the
SDA in the synthesis remains, however, enigmatic.
Using ab initio molecular dynamics (AIMD) simulations we investigate the effect
of some commonly used SDAs on the water network in their hydration layers. The
effects of charge and amine groups are investigated by comparison of amino
adamantine, methyl adamantane and protonated amino adamantane; we also compare
piperidine and methyl piperidine. We use a specifically developed code to
analyse the trajectory of the molecular dynamics simulations, in order to
search for the presence of rings of water in the hydration layers. The results
demonstrate how the nature of the SDA species (charged, neutral, presence of an
amine) affects the number and stability of different rings of water. These
findings have implications for the possible role of the formation of clathrate
hydrates in the nucleation of zeolites. In addition we investigate the
occurrence of different ring types within the vicinity of different moieties of
the SDAs, revealing the importance of a neutral amine group for the
stabilization of various rings.
“VAMPIRE: Advanced modelling of complex magnetic materials”
Richard Evans and Roy Chantrell
Lecture Theatre 22
Refreshments in the Turner Museum from 2.30
The continuing development of advanced magnetic nanomaterials for electronic devices and medical applications necessitates an understanding of magnetism at the atomistic, granular and macroscopic level – a true multi-scale problem. Computer simulation can give added insight to the fundamental physical properties of such nanomaterials and the interplay of effects at different length and timescales. At the nanoscale everything becomes complex – surfaces, crystallographic defects, interface mixing, surface roughness all have a bearing on the macroscopic magnetic properties of a material. Such phenomena can lead to strange spin states, magnetic reversal modes, temperature dependent properties making the physics of the nanoscale somewhat probabilistic. Even simple systems, such as isolated nanoparticles, in reality will show some size and shape variation, leading to a dispersion of the magnetic properties. In order to understand these effects detailed models of individual particles are still needed, but additionally the collective or large scale behaviour needs to be modelled presenting a much more significant problem. Due to the fundamental resolution of atomistic spin models, large scale simulations require a significant amount of computational effort, well beyond the capability of a single desktop computer.
VAMPIRE is a computer code which has been specifically developed to model these larger collective systems while retaining all the complex microscopic detail. In this talk I will outline the wide range of effects which can be simulated with the atomistic model and how they are implemented in VAMPIRE. I will also cover the computational strategies used to enable the code to run on supercomputing clusters and graphics cards. Finally I will present some immediate applications which will provide new insight into the magnetic behaviour of some of the most complex materials known today.
The next MESAS meeting will be at 3.30 Tuesday 30th March.
Presented by Dr Yvette Hancock of York University.
More details to follow…
The nest MESAS talk will be given by Dr Inna Gitman.
Tuesday 10th November 3.30pm LT22 in the Hadfield Building. Tea, coffee and cakes available from 3pm.
Multi-scale methods and the determination of Representative Volume Elements
in Solid Mechanics
Several different approaches are available in order to describe material behaviour. Considering material on the higher (macro) level of observation constitutes the macroscopic approach. However, the key to understand a macro materials behaviour lies in its meso-structure. As such the meso-scopic approach can be used, which is based on the detailed material description of the lower (meso) observational level. The main focus of this presentation is the combination of the two above techniques: the multi-scale approach. The idea is, by means of a hierarchical multi-scale procedure, to bring the homogenised information of the detailed meso-structural description to the macro-level in the form of effective properties. Thus, the homogeneous macro-structural behaviour is driven by the heterogeneous meso-structure. Traditionally, the size of a Representative Volume Element (RVE) of the material on the meso-level is chosen as a model parameter within the multi-scale framework. Two questions arise: what should this size be and how stable is this multi-scale model based on an RVE? As an answer to the first question, we propose a unique procedure to determine the RVE size. With knowledge of the RVE size, the multi-scale procedure can be introduced, in which the meso-level RVE plays the role of a macro-level length-scale parameter. However, the answer to the second question is not always positive. As an example the material behaviour due to mechanical loading can be considered. Although the results are stable and reliable in the linear-elastic and hardening regimes, the picture changes in softening. This is caused by the material developing strain localisation and as a consequence losing its statistical homogeneity. For such a material a Representative Volume cannot be found and as an inference cannot be used in the multi-scale framework. A conceptually new so-called coupled-volume multi-scale approach is introduced, based on abandoning the separation of scales principle. This approach does not require an RVE be a model parameter. The idea of the approach is to uniquely link the size of the meso-structural unit cell and element size of the discretised macro-structure. The results of this coupled-volume approach show stable and reliable behaviour in all mechanical regimes.
Welcome to the MESAS homepage!
We are a group of modellers and simulators based in the Department of Engineering Materials at Sheffield Univeristy. This website gives details of our research, software development and upcoming seminar talks. Please explore!