Regensburg 2016 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 41: Methods in Computational Materials Modelling I: Ab initio thermodynamics
MM 41.3: Vortrag
Mittwoch, 9. März 2016, 16:15–16:30, H52
Including DFT data in phase diagram calculations for zirconium carbide — •Theresa Davey1, Andrew Duff1, Suzana Fries2, and Michael Finnis1,3 — 1Department of Materials, Imperial College London, London SW7 2AZ, UK — 2ICAMS, Ruhr-Universität Bochum, 44801 Bochum, Germany — 3Department of Physics, The Thomas Young Centre, Imperial College London, London SW7 2AZ, UK
The CALPHAD approach takes experimental data and parameterises Gibbs energy curves with an optimal fit to this data, which can be phase boundary measurements or thermodynamic data. Thermo-Calc, and other phase diagram assessment codes, make no reference to the vacancy formation energy explicitly, leaving it only to be referred to implicitly within the Gibbs energy formulation [1]. Nevertheless, vacancy formation energies must significantly affect the phase stability when compounds are not strictly stoichiometric.
In recent years, theoretical calculations of the vacancy formation energy (or other point defect formation energies), which are difficult or impossible to measure experimentally, have been produced. This data could be used to increase the physical information encoded within a thermodynamic database.
For the zirconium-carbon phase diagram, I show how data from DFT calculations of the vacancy formation energy in the zirconium carbide phase can introduced as a constraint on the parameterisation of the Gibbs energy, and how this changes the resulting phase diagram.
[1] J. Rogal et al. (2014), Phys. Status Solidi B, 251(1) 97-129.