Maroudas, Dimitrios

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Professor, Department of Chemical Engineering
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Chemical Engineering
Computational Materials Science
Electronic Materials and Nanostructures
Materials for Renewable Energy Technologies
Multiscale Modeling of Complex Systems
Our research interests are in the area of multi-scale modeling of complex systems with special emphasis on theoretical & computational materials science & engineering. Our research program aims at simulation of processing and function and prediction of structure, properties, and reliability of electronic and structural materials. In addition to obtaining a fundamental understanding of the behavior of complex material systems, we are especially interested in modeling processing and function of semiconductor and metallic thin films used in the fabrication of electronic, optoelectronic, and photovoltaic devices. All of these material systems are characterized by structural inhomogeneities, such as crystalline lattice imperfections, surfaces, interfaces, and a variety of nanostructural features. Understanding the formation and evolution of such nano/micro-structure during physical or chemical processing and during device function is particularly important in developing processes that yield optimal material properties and guarantee device performance and reliability. Our research efforts focus on the development and implementation of computational quantum, statistical, and continuum mechanical methods for the study of structure and dynamics and for predictions of bulk and interfacial properties of heterogeneous materials. Special emphasis is placed on establishing rigorous links between atomistic and macroscopic (continuum) length scales and between fast and slow time scales: this enables us to develop coarse descriptions of multi-scale, multi-physics phenomena in complex materials starting from an atomistic, first-principles-based description of bonding and dynamics. Consequently, our research employs computational methods that span the spectrum from electronic structure calculation techniques to continuum numerical modeling, including: ab initio calculations of atomic structure, total energy, and atomic-scale dynamics based on density functional theory; structural relaxation, lattice-dynamics, Monte Carlo, and molecular-dynamics simulation methods based on empirical and semi-empirical descriptions of interatomic interactions; kinetic Monte Carlo and mean-field rate equation models; and continuum modeling techniques based on domain discretization such as finite-element, finite-difference, and boundary-element methods. In addition, analytical and numerical stability & bifurcation theory are implemented for understanding materials’ structural and morphological response upon variation of processing and operating parameters. Currently, we are especially interested in developing methods for overcoming time-scale limitations of atomistic dynamical simulators and enabling such simulators to perform numerical bifurcation & stability analysis.

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  • Publication
    A Comparison of the Elastic Properties of Graphene- and Fullerene-Reinforced Polymer Composites: The Role of Filler Morphology and Size
    (2016-01-01) Lu, Chang-Tsan; Weerasinghe, Asanka; Maroudas, Dimitrios; Ramasubramaniam, Ashwin
    Nanoscale carbon-based fillers are known to significantly alter the mechanical and electrical properties of polymers even at relatively low loadings. We report results from extensive molecular-dynamics simulations of mechanical testing of model polymer (high-density polyethylene) nanocomposites reinforced by nanocarbon fillers consisting of graphene flakes and fullerenes. By systematically varying filler concentration, morphology, and size, we identify clear trends in composite stiffness with reinforcement. To within statistical error, spherical fullerenes provide a nearly size-independent level of reinforcement. In contrast, two-dimensional graphene flakes induce a strongly size-dependent response: we find that flakes with radii in the 2–4 nm range provide appreciable enhancement in stiffness, which scales linearly with flake radius. Thus, with flakes approaching typical experimental sizes (~0.1–1 μm), we expect graphene fillers to provide substantial reinforcement, which also is much greater than what could be achieved with fullerene fillers. We identify the atomic-scale features responsible for this size- and morphology-dependent response, notably, ordering and densification of polymer chains at the filler–matrix interface, thereby providing insights into avenues for further control and enhancement of the mechanical properties of polymer nanocomposites.