  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 microscopic equations of motion. This
framework allows us to make specific predictions pertaining to the mechanical
properties which we can validate through deformation experiments performed in
Molecular Dynamics simulations.
