Collaborative Research: Mesoscopic Defect Field Interactions in Materials with High Number Density of Interfaces

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Deformation behavior of crystalline materials is highly complex, owing to a hierarchy of length scales that describes their structural makeup. Interfaces link distinct crystal structures or material phases at these various length scales. The interactions of crystalline defects with interfaces are chiefly responsible for the emergent material behavior at the application scale. The collective interactions of defects and interfaces through multiple scales up to the higher scale of everyday applications have been extremely challenging to resolve experimentally and have also not been captured using computer simulations to the desired sophistication. This is a significant obstacle to the understanding of the behavior of complex materials, where high density of specific interfaces is instrumental in achieving superior functional and/or mechanical properties. This research aims to address this challenge through the study of superlattices and metamaterials by exploiting and further advancing an atomistic-to-continuum scale method. It is expected that this research will significantly promote the fields of mechanics of materials and computational materials science, with commensurate impact on the rapidly developing field of computational materials design, which will advance national health, prosperity, and welfare. This work is also expected to have substantial broader impact through training of undergraduate students in high-performance computing, graduate curriculum enhancements, and dissemination of codes to the wider community. The project will also reach out to engage students from underrepresented groups.Superlattices and metamaterials represent two emerging material systems that derive their exceptional properties from structure rather than composition. With their well-ordered periodic interfaces and structure, superlattices and metamaterials provide model systems amenable to systematic study of the collective role of interfaces on evolving defect structures. The goal of this collaborative effort is to demonstrate the collective role of interfaces and defects on mechanical properties by studying this special class of material systems by using an advanced Concurrent Atomistic-Continuum (CAC) approach. It is expected that this research will identify the dominant deformation mechanisms as well as the key structural variables that control the materials behavior and the underlying mechanisms, explore the critical length scale or structural parameters at which the materials exhibit a transition from ductile to brittle behavior, and investigate the fundamental phenomena that control the plastic flow and fracture behaviors in these material systems.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.