CAREER: Energy Landscape Based Tools for Modeling Materials at the Nanoscale

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(CAREER) Energy Landscape Based Tools for Modeling Materials at the NanoscaleProject SummaryMaterials 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 featureprominently 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 ofmechanical failure. The technological relevance of these issues for solid materials has long beenappreciated in industrial settings because many applications require micro- or nanoscale componentsthat can exhibit mechanical integrity over a broad range of conditions. Unfortunately, acomprehensive 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 theeffects of confinement on a material's potential energy landscape. Although energy landscapes havebeen 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 basedformalism.Based on the success of these studies, the PI'spropose to fully develop and apply this approach in atwo-pronged research program that will allow us to address systems of experimental relevance. Thefirst part calls for using landscape based simulation methods to probe the molecular-levelprocesses that control deformation, yielding, and failure in bulk and nanoconfined metallicglasses. This study will help to elucidate how interfaces and confinement impact the novel mechanicaland structural responses of metallic glasses to various types of loading. The models are propose toinvestigate and provide guidance into the potential mechanical behavior of metallic glasses innanocomposite materials. The second proposed effort is the development of a new approach thatcombines the energy landscape framework with classical density functional theory (DFT) forinhomogeneous fluids. The resulting landscape based DFT will provide new predictions for thebehavior of both liquid and glassy states in nanoconfined environments. The proposed work willprovide a sound foundation for collaborations to study dynamic fracturing of nanoscale glasses viaexperiments and large-scale simulations. The PI's also propose an associated education plan that willengage 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 ofeductational tool called a theory-driven learning module. This module can be readily created withmethods that are routinely used in the PI's research group, illustrating a practical benefit of integratingteaching and research. Finally, a novel outreach program is outlined that will bring leaders of Austin'stechnology sector into the K-12 classrooms of smaller Texas towns.Broader Impacts. The research methods introduced here could lead to significant improvementsin the understanding of material stability at the nanoscale. This understanding is urgently neededbecause the current lack of knowledge presents a formidable barrier to conceiving new nanoscaleprocesses and designing nanostructured materials for use in advanced material, biomedical, andsemiconductor applications. These applications, ranging from stronger composite materials to smallerand faster computers, would substantially impact the economy and the everyday lives of millions. Theresearch is integrated with broader initiatives that seek not only to enhance the educational experienceof students at all levels, but also to inform the public about science, engineering, and the careeropportunities in both. The plan recognizes that engineers are increasingly involved in developingprocesses that must perform robustly on small length scales, and it introduces both courses andeducational tools that will prepare them for this challenge. The novel K-12 outreach program that isproposed will serve as a means for engaging the public in a meaningful dialogue about the societalimpact of science and the possibilities of engineering and science "as a career".