Computational Study of Nanomaterials: From Large-Scale Atomistic Simulations to Mesoscopic Modeling

Abstract

Definitions Nanomaterials (or nanostructured materials, nano-composites) are materials with characteristic size of structural elements on the order of less than several hundreds of nanometers at least in one dimension. Examples of nanomaterials include nanocrystalline materials, nanofiber, nanotube, and nanoparticle-reinforced nanocomposites, and multilayered systems with submicron thickness of the layers. Atomistic modeling is based on atoms as elementary units in the models, thus providing the atomic-level resolution in the computational studies of materials structure and properties. The main atomistic methods in material research are (1) molecular dynamics tech-nique that yields " atomic movies " of the dynamic mate-rial behavior through the integration of the equations of motion of atoms and molecules, (2) Metropolis Monte Carlo method that enables evaluation of the equilibrium properties through the ensemble averaging over a sequence of random atomic configurations generated according to the desired statistical-mechanics distribu-tion, and (3) kinetic Monte Carlo method that provides a computationally efficient way to study systems where the structural evolution is defined by a finite number of thermally activated elementary processes. Mesoscopic modeling is a relatively new area of the computational materials science that considers mate-rial behavior at time-and length-scales intermediate between the atomistic and continuum levels. Mesoscopic models are system-/phenomenon-specific and adopt coarse-grained representations of the mate-rial structure, with elementary units in the models designed to provide a computationally efficient representation of individual crystal defects or other elements of micro/nanostructure. Examples of the mesoscopic models are coarse-grained models for molecular systems, discrete dislocation dynamics model for crystal plasticity, mesoscopic models for nanofibrous materials, cellular automata, and kinetic Monte Carlo Potts models for simulation of micro-structural evolution in polycrystalline materials.