(CAREER) Energy Landscape Based Tools for Modeling Materials at the Nanoscale
Project Summary Materials confined to small dimensions often behave differently than in the bulk. In particular, they exhibit thermodynamic, kinetic, and mechanical limits of stability that depend on sample size, shape, and the physical characteristics of their interfaces. Property modifications that feature prominently in 'nanoconfined' systems include the appearance of surface-induced phase transitions, shifts of the bulk glass transition temperature, and the emergence of interface-mediated modes of mechanical failure. The technological relevance of these issues for solid materials has long been appreciated in industrial settings because many applications require micro- or nanoscale components that can exhibit mechanical integrity over a broad range of conditions. Unfortunately, a comprehensive theoretical approach for predicting these effects has been slow to develop. Intellectual Merit. The PI propose to introduce a new theoretical framework based on exploring the effects of confinement on a material's potential energy landscape. Although energy landscapes have been primarily used to study biomolecules, small molecular clusters, and bulk materials, they argue that they are particularly well suited to provide insights into the implications of nanoscale confinement for materials. Specifically, the hypothesis is that the stability of glassy nanostructures (relative to the bulk) can be understood in terms of how confinement changes their energy landscapes. To test this idea, the PI's have performed several "proof of concept" studies for our new landscape based formalism. Based on the success of these studies, the PI'spropose to fully develop and apply this approach in a two-pronged research program that will allow us to address systems of experimental relevance. The first part calls for using landscape based simulation methods to probe the molecular-level processes that control deformation, yielding, and failure in bulk and nanoconfined metallic glasses. This study will help to elucidate how interfaces and confinement impact the novel mechanical and structural responses of metallic glasses to various types of loading. The models are propose to investigate and provide guidance into the potential mechanical behavior of metallic glasses in nanocomposite materials. The second proposed effort is the development of a new approach that combines the energy landscape framework with classical density functional theory (DFT) for inhomogeneous fluids. The resulting landscape based DFT will provide new predictions for the behavior of both liquid and glassy states in nanoconfined environments. The proposed work will provide a sound foundation for collaborations to study dynamic fracturing of nanoscale glasses via experiments and large-scale simulations. The PI's also propose an associated education plan that will engage the public in a dialogue about the modern roles of computing and nanoscience in engineering. It does so by introducing new undergraduate and graduate level courses and a new type of eductational tool called a theory-driven learning module. This module can be readily created with methods that are routinely used in the PI's research group, illustrating a practical benefit of integrating teaching and research. Finally, a novel outreach program is outlined that will bring leaders of Austin's technology sector into the K-12 classrooms of smaller Texas towns. Broader Impacts. The research methods introduced here could lead to significant improvements in the understanding of material stability at the nanoscale. This understanding is urgently needed because the current lack of knowledge presents a formidable barrier to conceiving new nanoscale processes and designing nanostructured materials for use in advanced material, biomedical, and semiconductor applications. These applications, ranging from stronger composite materials to smaller and faster computers, would substantially impact the economy and the everyday lives of millions. The research is integrated with broader initiatives that seek not only to enhance the educational experience of students at all levels, but also to inform the public about science, engineering, and the career opportunities in both. The plan recognizes that engineers are increasingly involved in developing processes that must perform robustly on small length scales, and it introduces both courses and educational tools that will prepare them for this challenge. The novel K-12 outreach program that is proposed will serve as a means for engaging the public in a meaningful dialogue about the societal impact of science and the possibilities of engineering and science "as a career".
