at the atomic scale, solids can be modeled by molecular mechanics or molecular dynamics, which have become very useful tools in studying crystal structure, defect dynamics and material properties. however due to the computational complexity, the application of these models are usually limited to very small spatial and temporal scales. on the other hand continuum models, such as elasticity, elastodynamics and their finite element (or finite volume) formulations, have been widely used to study processes at much larger scales. but the constitutive relation involved in these continuum models may be ad hoc, and fails to count for the presence of microstructure in the material. /vskip .1in \noindent in this talk i will present a multiscale model, which couples the atomistic and continuum models concurrently. the macroscale model evolves the system at continuum scale, and the atomistic model, which only involves a small number of atoms, estimate the constitutive data and defect structure. i will show the estimate of the modeling error as well as various applications of this new model.