McKenna Materials Modelling Group

Research overview

The McKenna Materials Modelling Group is based in the Department of Physics at the University of York. Our research is unified under the general theme "modelling the properties of surfaces and interfaces". In recent work we have focused on nanometre sized and nano-structured systems, such as nanoparticles, nanopowders and thin film heterostructures, which possess unique properties (e.g. electronic, magnetic, optical and chemical) and have wide-ranging applications in fields such as electronics, catalysis, energy and medicine. There is constant demand for improved functionality of these systems and theoretical modelling plays a vital role. We address these problems, in close collaboration with experiment, by developing and employing a range of multi-scale theoretical and computational techniques to model the relevant conditions (i.e. temperature and pressure) and characteristic scales (e.g. time and length) relevant to real applications. More information on some of our main research areas can be found below.

  • Vacancies

    PhD position now available in our group.

  • TiN(310)[001] tilt grain boundary.

    Cover of Journal of Applied Physics: Structure and properties of a TiN grain boundary'.

  • Grain boundaries in solar absorbers.

    New EPSRC-funded project on High-throughput screening of polycrystalline solar absorbers.

  • Anti-site boundary defect characterisation of Cu2ZnSnSe4.

    Crystal structure and anti-site boundary defect characterisation of Cu2ZnSnSe4.

  • L10 FePt nanoparticles supported on Mg(Ti)O.

    Morphology of L10 FePt nanoparticles supported on Mg(Ti)O for heat-assisted magnetic recording applications.

  • Atomic structure and electronic properties of MgO grain boundaries in tunnelling magnetoresistive devices.

    Atomic structure and electronic properties of MgO grain boundaries in tunnelling magnetoresistive devices.

  • CTDSI workshop.

    Workshop on Charge Trapping Defects in Semiconductors and Insulators.

  • Charge trapping at nanoparticle interfaces.

    New EPSRC-funded project on Optimisation of charge carrier mobility in nanoporous metal oxide films.

  • Modification of charge trapping at particle/particle interfaces in TiO2.

    Modification of charge trapping at particle/particle interfaces in TiO2.

  • Computational Modeling of Inorganic Nanomaterials.

    New book on Computational Modeling of Inorganic Nanomaterials.

  • Atomic structure of the CoFe/MgO interface. Experimental electron microscopy image (left) and simulated image based on first principles theoretical prediction (right).

    Atomic structure and interdiffusion in CoFeB/MgO/CoFeB magnetic tunnel junctions.

  • Atomic structure of the (111) twin defect in Fe3O4

    Atomic structure of twin growth defects in magnetite.

  • Electron trapping at the surface of a titanium dioxide nanocrystal

    Electron trapping on the surface of titanium dioxide nanocrystals.

  • Atomic structure of a dislocation in MgO

    Polymorphism of the atomic structure of edge dislocations in MgO revealed by predictive modelling and electron microscopy.

  • Simulation of electron transport through an interface between titanium dixoide crystallites

    Simulation of electron transport through an interface between titanium dixoide crystallites showing the impact of charge trapping on mobility.

  • Experimental and theoretically predicted high-resolution electron microscopy images of the (110) antiphase boundary defect in magnetite

    Experimental and theoretically predicted high-resolution electron microscopy images of the (110) antiphase boundary defect in magnetite.

  • Dissociation of a H atom into an adsorbed proton and electron at a surface terminated screw dislocation in MgO

    Dissociation of a H atom into an adsorbed proton and electron at a surface terminated screw dislocation in MgO.

  • 3D electron tomographic reconstruction of nanoporous gold

    Three-dimensional electron tomographic reconstruction of the nanoporous gold structure which exhibits high catalytic activity.

  • Two-dimensional localisation of hole polarons

    Prediction of the two-dimensional localisation of hole polarons in the metal oxide material hafnium dioxide.

Polycrystalline materials

Polycrystalline materials are common in nature and find applications in many different areas of science and technology. Grain boundary defects (i.e. interfaces between crystal grains) play a key role in determining many materials properties but are in many cases poorly understood. To help address this important problem we are developing first-principles based computational methods to predict the atomic-scale structure and properties of grain boundary defects. Working closely with experimental collaborators (Prof. Ikuhara, Univ. Tokyo) we have helped reveal the structure of grain boundaries in a wide range of materials (including MgO, HfO2, Si and TiO2) with relevance to applications in microelectronics, spintronics, catalysis, surface science and electron transport in solar cell materials.

Metal-oxide electronics

Metal-oxide materials are at the heart of a number of current and emerging device technologies with applications in areas such as logic, data storage, optoelectronics and sensing. Atomic-scale defects in oxide materials are often detrimental to performance but in some cases can be essential for realising functionality. We are developing and applying approaches to predict the properties and dynamics of defects in oxide materials in order to drive improvements in device performance. For example, in recent work we have helped understand the resistive switching effect in HfO2 which can be used for a non-volatile and energy-efficient memory technology. We are also investigating the role of defects in oxides such as Fe3O4 and MgO with relevance to spintronic device applications.

Electron trapping

In many materials atomic-scale defects such as vacancies, interstitials and impurities are able to trap electrons and therefore play a critical role in determining electronic, chemical and optical properties. In materials with large electron-phonon coupling electrons can even self-trap in the perfect lattice forming small polarons. Such effects underpin a range of fundamental and applied issues including superconductivity, magnetism, electron transport in semiconductors and photocatalysis. We are employing a range of self-interaction corrected quantum-mechanical approaches to accurately model electron and hole trapping in nanostructured materials (including surfaces and interfaces).

Oxide nanopowders

Metal oxide nanopowders comprising a porous network of interconnected nanocrystals represent an interesting class of system with broad applications in chemistry, energy materials, sensing and optical materials. In a long-running collaboration (Prof. Diwald, Univ. Salzburg) we have helped to understand the electronic and optical properties of MgO nanopowders and investigated means to modify them in a controlled way via doping. Our studies have helped elucidate the role of nanocrystal interfaces as charge trapping and luminescence sites and demonstrated the potential of doped MgO nanopowders as luminescent materials for solid state lighting.

Dynamic nanoparticles

Dynamical interactions between nanoparticles and surrounding molecules can induce both overall morphology transformations and atomic scale fluctuations in their structure. As a consequence properties (optical, electronic and chemical, for example) can be significantly different from those predicted by simple models. This is important for numerous technological applications in areas such as catalysis, gas sensing, and drug delivery, and also for the interpretation of fundamental studies in nanotechnology. We are developing computational approaches to model these effects and recent work has demonstrated how gold naoparticles can be reshaped by adsorption of carbon monoxide molecules.