Based on the notion of micro-structure in linear elasticity presented by Mindlin, a new extended continuum mechanics (ECM) formulation is derived which can be utilized to model the material behavior at atomic scale. An attempt has been made to present a formulation capable of producing the molecular dynamics (MD) simulation results with less computational effort. To this end, some new kinematical variables are defined and some constitutive relations are obtained from MD. To validate the proposed ECM formulation, it is applied to a properly defined sample problem and the response is compared with the MD simulation result and the classical continuum mechanics (CCM) solution.