Structure and dynamics of complex metallic alloys studied by numerical simulation

在项目的前一阶段，我们已经研究了简化模型势，原子相互作用的特征导致了复杂结构的形成。此外，通过应用团簇位置的平铺模型并将其提升到超空间，我们可以建立对Al-Pd-Mn的所有ǫ相及其基本相变缺陷及其偏位的形式和运动的粗粒度统一描述。在目前的项目期间，我们打算与实验者密切合作，确定原子尺度上的结构细节。通过X射线散射和高分辨率电子显微镜获得的基本ξ和ǫ6相的原子位置、它们的五角形-非角形相子缺陷和它们的偏位核的数据将通过分子动力学和从头计算的组合得到精炼。此外，对于一系列结构越来越复杂的镁锌化合物，这种复杂性对原子动力学的影响应通过对动态结构因子等可观测值的数值计算来研究。在笼状化合物的结构确定方面也将给予其他合作伙伴支持。经典模拟的先决条件是仔细确定相互作用势，其参数将部分符合量子力学从头计算的结果。

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.