TECHNICAL EXPLANATION: The Division of Materials Research and the Division of Mathematical Sciences contribute funding to this award which falls under the NSF-wide Mathematical Sciences Priority Area. This award supports computational and theoretical research and education seeking to elucidate the atomistic mechanisms of fracture and plasticity in nanocrystalline ceramics. Nanostructured silicon carbide (n-SiC) has high fracture toughness and diamond-SiC nanocomposites (n-C-SiC) have high hardness. Grain boundaries (GBs) play a crucial role in the deformation of nanocrystalline metals. The interfaces between the diamond nanoparticles and the SiC matrix in the n-C-SiC likely play a critical role in determining mechanical properties. The PI will perform multimillion-atom MD simulations of nanoindentation and fracture in n-SiC and n-C-SiC on parallel computers to understand atomistic mechanisms underlying high hardness and toughness. The PI plans to: Characterize the nucleation and kinetics of defects in response to mechanical loading. Determine the role of GB and bulk deformation. Identify the effect of GB structures (e.g., twin boundaries), GB diffusion and sliding, as well as of interfacial debonding on hardness and fracture toughness. The PI will also plans to develop and implement: Innovative data mining techniques, such as graph-based algorithms, to identify and track topological defects in the resulting massive multivariate datasets. A hybrid simulation scheme based on temperature accelerated MD, reconstruction of the potential energy landscape, and reaction path sampling to study rare events such as GB diffusion. The research program will be integrated with training and education activities. These include: 1) multidisciplinary training of undergraduate and graduate students involving both atomistic simulations and nano-experiments, 2) developing a course on "advanced simulations of materials at nanoscale", as part of the interdisciplinary degree of Materials Science Program and the new degree options in Computational Science and Nanoengineering in the Engineering Physics Department at the University of Wisconsin, (3) facilitating a cross-departmental curriculum in scientific modeling, and (4) developing campus-wide atomic-modeling seminar. NON-TECHNICAL EXPLANATION: The Division of Materials Research and the Division of Mathematical Sciences contribute funding to this award which falls under the NSF-wide Mathematical Sciences Priority Area. This award supports computational and theoretical research that seeks to understand how ceramic materials fracture and deform starting from the constituent atoms. The PI will focus on ceramic materials that are composed of many nanometer-sized grains. The PI will use large-scale computer simulation techniques involving millions of atoms with the aim of understanding how the hardness of specific materials depends on the size of the grains, how these materials deform when a mechanical stress is applied, and ultimately how to create a material that is both hard and highly resistant to fracture. The proposed research may have impact on the design and nanoengineering of superhard materials that have a broad range of applications. The proposed research also involves developing advanced computational tools including methods to enable simulation for long times and to identify specific arrangements of atoms involved in materials deformation. The research program will be integrated with training and education activities. These include the direct involvement of a graduate student in the research and developing interdisciplinary graduate and undergraduate level courses on advanced computer modeling of materials.
