Composite Grid Atomistic Continuum Method: An Adaptive Approach to Bridge Continuum with Atomistic Analysis

The Composite Grid Atomistic Continuum Method, a method to couple continuum and atomistic models, is proposed in a three-dimensional setting. In this method, atomistic analysis is used only at places where it is needed in order to capture the intrinsically nonlinear/nonlocal behavior of the material at the atomic scale, while continuum analysis is used elsewhere for efficiency. The atomistic model is defined on a separate grid that overlaps the continuum in selected regions. The atomistic and the smallest scale continuum model are connected by appropriately defined operators. The continuum model provides boundary conditions to the discrete model while the atomistic model returns correcting eigenstrains. The adaptive selection of the spatial regions where the atomistic correction is needed is made based on error indicators developed to capture the nonlinearity and nonlocality modeling errors. The method is applied to represent dislocation nucleation from crack tips and nanoindentation in aluminum.