A mesoscale framework for the modeling of defects and interfaces in crystals

• Applicant: Professor Dr. Marco Salvalaglio
• Subject Area: Computer-Aided Design of Materials and Simulation of Materials Behaviour from Atomic to Microscopic Scale ; Mechanical Properties of Metallic Materials and their Microstructural Origins ; Thermodynamics and Kinetics as well as Properties of Phases and Microstructure of Materials
• Term: since 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 447241406

This project addresses the mesoscale modeling of crystalline systems, such as polycrystals and crystalline heterostructures. It aims at i) delivering theoretical tools that bridge micro- and macroscopic features while studying crystals, ii) overcoming limitations in time and length scales of current state-of-the-art approaches, iii) enabling applications to technology-relevant crystalline systems and related open problems in materials science. It builds on the phase-field crystal (PFC) model, which provides convenient descriptions of crystals over relatively long (diffusive) time scales through a continuous periodic field representing the atomic density. We propose to exploit its amplitude expansion (APFC), which is a coarse-grained version of the PFC model still retaining some details of the atomic length scale, to tackle the macroscopic morphological evolution of crystals together with the description of defects and interfaces. The basic APFC model will be significantly extended to model properties of real materials, including complex crystal structures, alloys, and solving some long-standing limitations of the approach. The development of a hybrid PFC-APFC method is also planned. It will combine the atomistic resolution of PFC in specific regions (e.g., at defects) with coarser description elsewhere as conveniently achieved through the APFC model. Particular tasks are planned to deliver a thorough coarse-grained description of the dynamics and morphology of extended defects, such as defected interfaces between rotated grains. The results obtained with the proposed framework will be also compared with other methods such as molecular dynamics, discrete dislocation dynamics, and continuum approaches, allowing for a general assessment of the results and capabilities of the developed technique. Applications of the resulting APFC-based mesoscale framework are planned, such as i) mesoscale simulations of heteroepitaxial systems, ii) mesoscale modeling of the morphologies and motion of dislocations and grain-boundaries, iii) effective continuum descriptions of anisotropies and nonlinearities due to features of crystal lattices. This project accompanies the application for the DFG-Emmy Noether Programme. The interdisciplinary research environment at the hosting institution (TU-Dresden), involving, in particular, its Institute of Scientific Computing and the Dresden Center for Computational Materials Science, will support the research activity and facilitate the success of the envisioned research. The planned cooperation with top-level physicists and materials scientists, working mostly on material modeling but also experiments, is also a strategic asset of the project.

• DFG Programme: Independent Junior Research Groups