FOR 1509: Ferroic Functional Materials - Multiscale Modelling and Experimental Characterisation

该研究单位专注于铁性功能材料的连续力学建模和实验表征。特别感兴趣的是允许不同物理量之间的耦合的材料，例如电场和机械场、机械场和磁场或磁场和电场之间的耦合。因此，主要的重点是铁电体和铁磁体以及多铁性复合材料。功能材料的性质在不同的尺度上出现。有些存在于原子尺度上，例如磁化强度。其他的，例如电极化，存在于晶体的晶胞水平上。此外，某些材料只有当上述量在更大的长度尺度上耦合时才获得它们的功能特性，例如在多铁性复合材料的情况下。为了描述这些材料，研究股在多个层面上开展活动。活动跨越分子静力学，微观结构演变的建模，并通过使用合适的均质化技术的现象学描述。在这种情况下，较小尺度上的建模是下一个尺度上的建模的物理基础和动机。独立于所考虑的规模，所使用的算法的数值稳定性和鲁棒性起着关键作用。因此，研究股的目标是开发可靠和强大的建模工具的新质量，用于描述多尺度上复杂的非线性磁-电-机械相互作用。这将通过几个研究领域的合作来实现。一个主要的组成部分是通过使用原子方法，相场方法和基于弛豫的方法以及经典的连续方法在不同尺度上对微观结构演化进行建模。除此之外，功能材料的有效响应的确定是特别感兴趣的。这将通过开发合适的均质化技术来实现，该技术允许相邻尺度之间的过渡。当然，所有的模型都必须经过验证，所需的材料参数必须确定。这将通过测量磁-电-机械材料响应的代表性实验数据库来实现。

The Research Unit focusses on the continuum-mechanical modelling and experimental characterisation of ferroic functional materials. Of particular interest are materials, which allow for coupling between different physical quantities as for instance coupling between electrical and mechanical, mechanical and magnetic or magnetic and electrical fields. The main focus is thus on ferroelectrics and ferromagnetics as well as on multiferroic composites. The properties of functional materials emerge on different scales. Some exist on the atomic scale as, for example, the magnetisation. Others, as e.g. the electric polarisation, are present on the unit cell level of a crystal. Furthermore, some materials obtain their functional properties only when the above quantities couple over a larger length scale as for instance in case of multiferroic composites. In order to describe those materials, the Research Unit is active on multiple scales. The activity spans molecular statics, modelling of microstructure evolution, and the phenomenological description by using suitable homogenisation techniques. In this context, the modelling on the smaller scales serves as physical basis and motivation for modelling on the scale next in size. Independent on the considered scale, the numerical stability and robustness of the used algorithms play a key role. Thus, the goal of the Research Unit is to develop a new quality in reliable and robust modelling tools for the description of the complex, non-linear, magneto-electro-mechanical interactions on multiple scales. This will be achieved through collaboration in several fields of research. One major building block is the modelling of microstructure evolution on different scales by using atomistic methods, phase-field methods, and relaxation-based methods as well as classical continuum approaches. In addition to that, the determination of the effective response of the functional materials is of particular interest. This will be obtained by developing suitable homogenisation techniques that allow for a transition between neighbouring scales. Of course, all models have to be validated and needed material parameters have to be identified. This will be realised by measuring a representative experimental data-base of the magneto-electro-mechanical material response.