Non-affine heterogeneities and droplet fluctuations in an equilibrium crystalline solid

We show, using molecular dynamics simulations, that a two-dimensional Lennard-Jones solid is subject to droplet fluctuations characterized by {\em non-affine} deviations from local crystallinity. The fraction of particles in these droplets increases as the mean density of the solid decreases and approaches $\approx 20$% of the total number in the vicinity of the fluid-solid phase boundary. We monitor the geometry, local equation of state, density correlations and van Hove functions of these droplets and show that some of these droplets are fluid-like and compact, while some are glassy and string-like. We provide evidence that these non-affine heterogeneities should be interpreted as being droplet fluctuations from nearby, metastable minima.