ITR/AP: Collaborative Research - Enabling Microscopic Simulators to Perform System-Level Analysis

Research: An interdisciplinary research team, at four universities, is collaborating on this medium-size Information Technology Research (ITR) project aimed at systematically bridging the gap between microscopic descriptions of complex material systems and systems-level analysis of direct engineering importance. A mathematics-assisted computational methodology will be developed that will enable microscopic-level simulators to perform systems-level analysis directly, without the need to pass through an intermediate level description of the material system through macroscopic (partial differential or integro-differential) evolution equations. Specifically, an ensemble-averaged "coarse" time-stepper-based computational superstructure will be "wrapped around" state-of-the-art microscopic dynamic simulators, such as molecular dynamics, kinetic Monte Carlo, Lattice-Boltzmann or hybrid codes. This methodology will enable microscopic simulators to perform advanced systems-level analysis: stability, bifurcation, "coarse" integration, sensitivity, and control tasks, of complex, nonlinear distributed processes. The planned algorithms will run on massively parallel machines. The computational framework will consist of the following basic elements: (i) choice of statistics of interest (e.g. distribution moments) for describing the coarse behavior; (ii) "lifting" of a macroscopic initial condition to an ensemble of consistent microscopic configurations; (iii) evolution over the same (short) time period of each initial microscopic configuration in the ensemble according to a microscopic simulator that embodies the best current description of the physical system; (iv) averaging ("restriction") over the ensemble of the evolved microscopic configurations to provide a macroscopic evolved system state; and (v) execution of the previous three steps over a finite set of macroscopic initial conditions. This new approach is robust in its implementation and portable in its range of scientific and engineering applications. It has general applicability to all systems for which a macroscopic description is conceptually possible, yet unavailable in closed form. It circumvents the difficulty in obtaining and closing such macroscopic models, while computationally extracting precisely the information that would be obtained by a macroscopic model, had the model been available in closed form. This provides the link between ITR and a spectrum of application areas. Impact: The impact of the research will be on establishing a powerful and general link between state-of-the-art microscopic-level simulations and fast systems level analysis capabilities. Although the research focuses on specific problems in heterogeneous hard materials and complex fluids, the computational framework is applicable to a broad range of complex systems, including biological systems, their processing and function. Since it has the potential to revolutionize engineering systems-level analysis, it could have educational impact as well as furthering advances in microelectronics, bioinformatics and nanotechnology.