Coarse-grained atomistic modelling of free surfaces and interfaces with application to nanoindentation
The properties a material exhibits close to a free surface are different from those measured in the bulk. So the modeling of nanostructures must account for free surface related effects. The main goal of this research project is to model free surface related processes such as nanoindentation as a key experiment for material testing on different length scales. The approach used is a three-dimensional fully nonlocal quasi-continuum method which belongs to the family of concurrent multiscale methods.
The example in the figure above shows the simulation of a nanoindentation of a cube. According to the idea of the quasi-continuum method in regions where a high accuracy is needed, in this case underneath the indenter, a fully atomistic representation of the simulation domain is chosen, whereas in regions where the deformation gradients are small, i.e. far away from the indenter, the material is represented by sparse clusters of atoms. The properties of these clusters are interpolated into all regions of the domain by a finite-element approach. The color code represents the displacements in indentation direction in nanometers; the scale marks are also given in nanometers.
Fully atomistic representation of dislocations nucleating from the indented area. Colors are according to the centrosymmetry parameter (high in regions of disorder and approaching zero in regions of perfect crystalline order).