Simulations of mechanics and structure of nanomaterials --- from nanoscale to coarser scales

TL;DR

This paper reviews multiscale simulation techniques for nanomaterials, highlighting atomic-level insights into nanocrystalline copper deformation and discussing methods to connect phenomena across different length scales.

Contribution

It provides a detailed case study of nanocrystalline copper deformation and discusses multiscale modeling approaches for complex material behaviors.

Findings

Grain boundaries actively contribute to deformation.

Deformation mechanisms shift below 10-15 nm grain size.

Smaller grains can lead to softer nanocrystalline metals.

Abstract

We discuss how simulations of mechanical properties of materials require descriptions at many different length scales --- from the nanoscale where an atomic description is appropriate, through a mesoscale where dislocation based descriptions may be useful, to macroscopic length scales. In some materials, such as nanocrystalline metals, the range of length scales is compressed and a polycrystalline material may be simulated at the atomic scale. The first part of the paper describes such simulations of nanocrystalline copper. We observe how the grain boundaries contribute actively to the deformation. At grain sizes below 10-15 nm deformation in the grain boundaries dominate over the traditional dislocation-based deformation mechanisms. This results in a reversal of the normal grain size dependence of the yield stress: we observe that the material becomes softer when the grain size is reduced. The second part of the paper gives an overview over simulation techniques appropriate for problems too large to be treated in atomic-scale simulations, and how they can be combined to describe the interplay between phenomena at different length scales through multiscale modelling.