Structure and dynamics of complex metallic alloys studied by numerical simulation

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In the previous period of the project we have studied on simplified model potentials, what features of atomic interactions lead to complex structure formation. Furthermore, by applying tiling models for cluster positions and lifting them to hyperspace we could establish a coarse-grained unified description for all ǫ-phases of Al-Pd-Mn, their basic phasonic defects and the form and motion of their metadislocations. In the present project period we intend to determine – in close cooperation with experimentalists – the structural details on an atomistic scale. Data for atomic positions of the basic ξ- and ǫ6-phases, their pentagon-nonagon phason defects and their metadislocation cores gained from x-ray scattering and by high resolution transmission electron microscopy will be refined by a combination of molecular dynamics and ab-initio simulations. Furthermore, on a series of Mg-Zn compounds with increasing structural complexity, the influence of this complexity on atomic dynamics shall be investigated by numerical calculations of observables like the dynamical structure factors. Support to other partners will also be given in the structure determination of clathrates. Prerequisites for the classical simulations are careful determinations of interaction potentials whose parameters partially will be fitted to results of quantum mechanical ab-initio calculations.