Prof. Jorge Kohanoff

Professor in Applied Mathematics and Theoretical Physics


Jorge

Rm: DBB.01.014
☎: +44 (0) 28 9097 6032
@: j.kohanoff@qub.ac.uk

Atomistic Simulation Centre Department of Physics and Astronomy School of Mathematics and Physics Queen's University Belfast University Road Belfast BT7 1NN Northern Ireland

Degrees, Awards and Honours

    Interests

    • Computer simulation and electronic structure calculations in Condensed Matter, Chemical, and Biological Physics
    • Materials under irradiation
    • Materials under extreme conditions (high pressures and temperatures)
    • Chemical reactivity and proton transfer processes
    • Scientific software development

    Most Recent Publications

    1. Electron-induced hydrogen loss in uracil in a water cluster environment, Journal of Chemical Physics, 2014, 140, pp. 184313
      doi: 10.1063/1.4874841 Abstract
      Low-energy electron-impact hydrogen loss due to dissociative electron attachment (DEA) to the uracil and thymine molecules in a water cluster environment is investigated theoretically. Only the A′-resonance contribution, describing the near-threshold behavior of DEA, is incorporated. Calculations are based on the nonlocal complex potential theory and the multiple scattering theory, and are performed for a model target with basic properties of uracil and thymine, surrounded by five water molecules. The DEA cross section is strongly enhanced when the attaching molecule is embedded in a water cluster. This growth is due to two effects: the increase of the resonance lifetime and the negative shift in the resonance position due to interaction of the intermediate negative ion with the surrounding water molecules. A similar effect was earlier found in DEA to chlorofluorocarbons.

    2. Universal tight binding model for chemical reactions in solution and at surfaces. III. Stoichiometric and reduced surfaces of titania and the adsorption of waterhttp://dx.doi.org/10.1063/1.4874841, Journal of Chemical Physics, 2014, 141, pp. 044505
      doi: 10.1063/1.4890492 Abstract
      We demonstrate a model for stoichiometric and reduced titanium dioxide intended for use in molecular dynamics and other atomistic simulations and based in the polarizable ion tight binding theory. This extends the model introduced in two previous papers from molecular and liquid applications into the solid state, thus completing the task of providing a comprehensive and unified scheme for studying chemical reactions, particularly aimed at problems in catalysis and electrochemistry. As before, experimental results are given priority over theoretical ones in selecting targets for model fitting, for which we used crystal parameters and band gaps of titania bulk polymorphs, rutile and anatase. The model is applied to six low index titania surfaces, with and without oxygen vacancies and adsorbed water molecules, both in dissociated and non-dissociated states. Finally, we present the results of molecular dynamics simulation of an anatase cluster with a number of adsorbed water molecules and discuss the role of edge and corner atoms of the cluster.

    3. Universal tight binding model for chemical reactions in solution and at surfaces. II. Waterhttp://dx.doi.org/10.1063/1.4890492, Journal of Chemical Physics, 2014, 141, pp. 044504
      doi: 10.1063/1.4890343 Abstract
      A revised water model intended for use in condensed phase simulations in the framework of the self consistent polarizable ion tight binding theory is constructed. The model is applied to water monomer, dimer, hexamers, ice, and liquid, where it demonstrates good agreement with theoretical results obtained by more accurate methods, such as DFT and CCSD(T), and with experiment. In particular, the temperature dependence of the self diffusion coefficient in liquid water predicted by the model, closely reproduces experimental curves in the temperature interval between 230 K and 350 K. In addition, and in contrast to standard DFT, the model properly orders the relative densities of liquid water and ice. A notable, but inevitable, shortcoming of the model is underestimation of the static dielectric constant by a factor of two. We demonstrate that the description of inter and intramolecular forces embodied in the tight binding approximation in quantum mechanics leads to a number of valuable insights which can be missing from ab initio quantum chemistry and classical force fields. These include a discussion of the origin of the enhanced molecular electric dipole moment in the condensed phases, and a detailed explanation for the increase of coordination number in liquid water as a function of temperature and compared with ice—leading to insights into the anomalous expansion on freezing. The theory holds out the prospect of an understanding of the currently unexplained density maximum of water near the freezing point.

    All of Jorge's publications

    Primary Interests

    • Computer simulation and electronic structure calculations in Condensed Matter, Chemical, and Biological Physics
    • Materials under irradiation
    • Materials under extreme conditions (high pressures and temperatures)
    • Chemical reactivity and proton transfer processes
    • Scientific software development

    Current Interests

    • Radiation damage in biological systems
      With Maeve Smyth, Bin Gu, Emilio Artacho, Fred Currell, David Timson, Eric Suraud and Rodolphe Vuilleumier

    • Irradiation of ices on interstellar dust grains
      With Emmet McBride, Tom Millar, Tom Field and Bob McCullough

    • Irradiation of nuclear materials
      With Alfredo Correa, Alfredo Caro, Daniel Sanchez-Portal and Emilio Artacho

    • Development of tight-binding models for chemical reactivity in condensed phases
      With Tony Paxton, Sasha Lozovoi and Terence Sheppard

    • Hydrogen-bonded ferroelectrics
      With Giuseppe Colizzi, Sergio Koval, Jorge Lasave, Ricardo Migoni, and Erio Tosatti

    • Modelling and simulation of ionic liquids
      With Tristan Youngs, Carlos Pinilla, Mario Del Popolo, Claudio Margulis and Ruth Lynden-Bell

    • Electronic structure calculations with quantum nuclei

      • Ab initio and model Hamiltonian path integral simulations in quantum statistical mechanics

      • Wave function methods for nuclei combined with DFT for electrons
        With N. Gidopoulos, Ivan Scivetti, Alfredo Caro and David Hughes

    Expertise in numerical techniques

    • First-principles Molecular Dynamics and Monte Carlo
    • Hybrid quantum/classical simulations
    • Path integral Monte Carlo
    • Wave packet propagation
    • First-principles path integral simulations
    • Electronic structure:
      • Pseudopotential PW
      • Gaussians
      • Pseudopotential LCAO (and order N)