Berlin 2012 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 60: Computational Materials Modelling IX - Interfaces and Boundaries

MM 60.1: Talk

Thursday, March 29, 2012, 17:15–17:30, TC 006

Atomistic modelling of interfaces between cubic phases and complex phases in refractory metals — •Thomas Hammerschmidt, Miroslav Cak, Jutta Rogal, and Ralf Drautz — ICAMS, Ruhr-Universität Bochum, Bochum, Germany

Topologically close-packed (TCP) phases play in important role in many modern alloys and steels. The TCP phase stability can be attributed to an interplay of bandfilling effects and differences in atomic size. In order to shed light on the precipitation of TCP phases, we study their interfaces to cubic phases. Here, we have chosen the interfaces bcc-A15 and fcc-σ due to their technological relevance in W thin films and in Ni-based superalloys, respectively. We investigate the interface formation energy by atomistic simulations with electronic structure methods at different levels of coarse-graining. On the tight-binding level, we employ simple canonical models to investigate relations between band-filling and interface structure. On the level of bond-order potentials (BOP), an approximation to the tight-binding scheme, we employ recently developed parametrisations for refractory metals. With the analytic BOPs we observe that the interface energy of a commensurate interface of multiple unit cells is minimised by a coincidence-site-lattice arrangement. We then minimise the interface energy with respect to the number of atoms by directly employing the atom-resolved binding energies of the analytic BOP. Our observation of a more densely packed interface for increased bandfilling can be attributed to a decrease in the covalent character of the bonds.