Professor John Harding
MA PhD FRCS FinstP
Professor of Materials Simulation
Department of Materials Science and Engineering
Sir Robert Hadfield Building
Mappin Street, Sheffield, S1 3JD
Telephone: +44 (0) 114 222 5957
Fax: +44 (0) 114 222 5943
John Harding joined the Department in 2004 from the Department of Physics and Astronomy, University College London having previously worked at Harwell from 1978 to 1995.
Real crystals stop somewhere and the boundaries, whether surfaces, grain boundaries or more complex interfaces often determine the behaviour of materials. 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. I am a member of a consortium of Universities (Leeds, Sheffield, UCL, Warwick) that is investigating the mechanisms of crystallisation using both simulation and experiment.
The most spectacular example of controlling crystallisation 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. This work was funded through an EPSRC programme grant "Hard-soft materials: from understanding to engineering" and involved collaborations both within Sheffield, nationally and internationally. Further details can be found here.
A current project is using techniques and ideas developed during that grant to investigate environmentally benign methods of extracting rare earths (which are often critical minerals). Further details can be found using the link to the project SoS_RARE.
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.
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.
Links to key projects
- Crystallisation in the real world: Delivering control through theory and experiment
- SoS RARE: Multidisciplinary research towards a secure and environmentally sustainable supply of critical rare earth elements (Nd and HREE). See www.bgs.ac.uk/SoSRARE
- Modelling electroceramic materials, especially ferroelectrics and lithium battery cathode materials. See www.shef.ac.uk/ccl
Professional activities and recognition (current)
- EPSRC Peer Review College
- Organiser of the annual CCP5 International Summer School in Molecular Simulation 2008-13; lecturer 2004-present
- External examiner, Foundation Year, University of Newcastle
- Member of management committee, Materials Chemistry Consortium (ARCHER)
- Member of N8 High Performance Computing steering committee
Some recent key publications
- 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.
- 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.
- 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.
- 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 97(2014) 885-891.
- A. Archer, H.R. Foxhall, N.L. Allan, D.S.D. Gunn, J.H. Harding, I.T. Todorov, K.P. Travis and J.A. Purton; Order parameter and connectivity topology analysis of crystalline ceramics for nuclear waste immobilisation: J. Phys. Cond. Matt. 26 (2014) Art. 485011
- Y.Y. Kim, J.D. Carloni, B. Demarchi, D. Sparks, D.G. Reid, M.E. Kunitake, C.C. Tang, M.J. Duer, C.L. Freeman, B.Pokroy, K. Penkman, J.H. Harding, L.A. Estroff, S.P. Baker and F.C. Meldrum; Tuning hardness in calcite by incorporation of amino acids, Nature Mater. 15 (2016) 903-91
- B. DeMarchi, S. Hall, T. Roncal-Herrero, C.L. Freeman, J. Woolley, M.K. Crisp, J. Wilson, A. Fotakis, R. Fischer, B.M. Kessler, R.R. Jersie-Christensens, J.V. Olsen, J. Haile, J. Thomas, C.W. Marean, J. Parkington, S. Presslee, J. Lee-Thorp, P. Ditchfield, J.F. Hamilton, M.W. Ward, C.M. Wang, M.D. Shaw, T. Harrison, M. Dominguez-Rodrigo, R.D.E. MacPheel, A. Kwekason, M. Ecker, L.K. Horwitz, M. Chazan, R. Kroger, J. Thomas-Oates, J.H. Harding, E. Cappellini, K. Penkman and M.J. Collins; Protein sequences bound to mineral surfaces persist into deep time, eLife 5 (2016) Art e17092.
- R. Demichelis, N.A. Garcia, P. Raiteri, R. Innocenti-Malini, C.L. Freeman, J.H. Harding, and J.D. Gale; Simulation of Calcium Phosphate Species in Aqueous Solution: Force Field Derivation, J. Phys. Chem. B 122 (2018) 1471-1483.
Research Assistants (postdocs)
Dr Aaron Finney
Dr Santosh Kumar (from October 2018)
Ms Robyn Ward
- MAT1610 Introduction to Materials Chemistry
- MAT1410 Biomaterials I
- MAT1920 Cradle to ? Materials and the Environment
- MAT4600 Multiscale materials modelling
- MAT6666 Materials selection, properties and applications