Harding, John - University of Sheffield - Department of Materials Science and Engineering

个人简介

John Harding joined the Department in 2004 from the Department of Physics and Astronomy, University College London having previously worked at Harwell since 1978. -

研究领域

Real crystals stop somewhere and the boundaries, whether surfaces, grain boundaries or more complex interfaces often determine the behaviour. This is particularly true for nanomaterials, where a significant fraction of the atoms are at a boundary. The way crystals grow, their shape and structure is determined by the local environment. The most spectacular example of this is the ability of living systems to grow minerals in complex shapes and sometimes unusual phases. Often, biominerals are nanocomposites – the combination of organic scaffold and mineral produces a material with unusual properties – for example the hardness of tooth enamel. We work closely with experimental groups, using simulations to understand how biomaterials are formed and why they have the properties that they possess. We also work with colleagues in the cell-mineral centre on how cells bind to minerals; a problem with applications from bio-remediation to bio-mining. This work is funded through an EPSRC programme grant "Hard-soft materials: from understanding to engineering" and involves collaborations both within Sheffield, nationally and internationally. Further details can be found on the link below. We have simulated the properties of interfaces as part of an EU programme to develop a multi-scale modelling framework for solar cells (Hipersol). This requires understanding the properties of the interfaces between the silver contact and silicon and also between the passivation layer and silicon and integrating this into a model of the solar cell. Further details can be found on the Hipersol link below. The bulk properties of crystals, particularly transport properties, are often determined by point defects, either intrinsic, deliberately added or just happen to be there. Understanding the behaviour of defects, interfaces and how they control crystal properties needs simulation at the atomic scale (and often at longer scales as well). We use simulations to understand the properties of a variety of electroceramics, working with other members of the Ceramics and Composites Laboratory. A combination of atomistic and finite element methods is used to model experimental impedance data without the necessity of using over-simplified models of the grain boundary structure and equivalent circuits. Simulations are also being used to help develop new materials for encapsulating high-level nuclear waste by looking at the effects of radiation damage on several candidate materials in collaboration with Daresbury Laboratory and the University of Bristol. New methods of topological analysis have been developed that show that metamict minerals are much more ordered than previously believed. In all these projects, the group therefore uses a variety of methods: static lattice calculations, molecular dynamics, kinetic Monte Carlo, quantum (ab initio) methods, mesoscale (coarse-grained) and finite element simulations in conjunction with experiment to try and understand materials at all appropriate length and timescales.

近期论文

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C. L. Freeman, F. Claeyssens, N.L. Allan and J.H. Harding, ‘Graphitic nanofilms as precursors to wurtzite films: theory’, Phys. Rev. Lett. 96 (2006) 066102. R. Carter, J. Sloan, A.I. Kirkland, R.R.Meyer, P.J.D. Lindan, G. Lin, M.L.H. Green, A. Vlandas, J.L. Hutchison and J. Harding, Correlation of structural and electronic properties in a new low-dimensional form of mercury telluride, Phys Rev Lett 96 (2006): Art. No. 215501. J. H. Harding, D.M. Duffy, M. Sushko, P.M. Rodger, D. Quigley and J.A. Elliott, Computational Techniques at the organic-inorganic interface in biomineralisation. Chem. Rev. 108 (2008) 4823-4854. M.L. Sushko, J.H. Harding, A.L. Shluger, R.A. McKendry and M. Watari; Physics of nanomechanical biosensing on cantilever arrays; Advanced Materials 20 (2008) 3848-3853. Mingjun Yang, S. L. Svane Stipp and John Harding; Biological Control on Calcite Crystallization by Polysaccharides; Crystal Growth & Design 8 (2008) 4066-4074. D. Quigley, P. M. Rodger, C. L. Freeman, J. H. Harding, and D. M. Duffy; Metadynamics simulations of calcite crystallization on self-assembled monolayers; J. Chem. Phys. 131 (2009) 094703. C.L. Freeman, J.H. Harding, D. Quigley and P.M. Rodger, Structural control of crystal nuclei by an eggshell protein. Angew. Chim. Intl. 49 (2010) 5135-5137 D. Quigley, C.L. Freeman, J.H. Harding and P.M. Rodger, Sampling the structure of calcium carbonate nanoparticles with metadynamics. J. Chem. Phys. 134 (2011) 044703. K.T. Butler, P.E. Vullum, A.M. Muggerud, E. Cabrera and J.H. Harding; Structural and electronic properties of silver/silicon interfaces and implications for solar cell performance; Physical Review B 83 (2011) 235307 C.L. Freeman, J.A. Dawson, J.H. Harding, Liu-Bin Ben and D.C. Sinclair; The Influence of A-Site Rare Earth Ion Size in Controlling the Curie Temperature of Ba1−xRExTi1−x/4O3; Adv. Func. Mater. 23 (2013) 491-495. J.S. Dean, J.H. Harding and D.C. Sinclair;Simulation of Impedance Spectra for a Full Three Dimensional Ceramic Microstructure Using a Finite Element Model; J. Amer. Ceram. Soc (2013); DOI: 10.1111/jace.12750