Elasticity in crystals with a high density of local defects: Insights from ultra-soft colloids

In complex crystals close to melting or at finite temperatures, different types of defects are ubiquitous and their role becomes relevant in the mechanical response of these solids. Conventional elasticity theory fails to provide a microscopic basis to include and account for the motion of point defects in an otherwise ordered crystalline structure. We study the elastic properties of a point-defect rich crystal within a first principles theoretical framework derived from the microscopic equations of motion. This framework allows us to make specific predictions pertaining to the mechanical properties that we can validate through deformation experiments performed in molecular dynamics simulations.