Dresden 2014 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 49: Computational Materials Modelling VII - Grain boundaries & Interfaces

MM 49.3: Talk

Thursday, April 3, 2014, 10:45–11:00, IFW D

Ab-initio prediction of the critical thickness of a precipitate in molybdenum — •Sankari Sampath and Rebecca Janisch — ICAMS, RUB, Bochum, Germany

The precipitation of new phases in a host metal or metallic alloy has a strong influence on the mechanical properties of the material. This precipitation leads to the formation of an interface that can be coherent, semi-coherent or incoherent with the host material. The calculation of coherent interface energies based on atomistic models is well established, but semi-coherent interfaces still present a challenge. Current approaches usually combine ab-initio data and continuum elasticity methods, while we now present a model for a semi-coherent interface completely based on ab-initio density functional theory calculations.

Our example is a metastable Mo-C phase, the body-centered tetragonal structure, which exists as a semi-coherent precipitate in body-centered cubic molybdenum. For the coherent interface, a standard supercell approach is used. The energy of the semi-coherent interface is calculated taking into account different contributions from the elastic strain energy stored in the precipitate, the misfit energy due to the misfit dislocation, and the chemical energy due to the bonding at the interface. By comparing the energy of a coherent with that of a semi-coherent precipitate as a function of thickness, we predict a critical thickness of the precipitate before it becomes semi-coherent that agrees well with the experimental observation.