Small defects in a crystal, whether an ice cube or cocoa butter, cause it to melt from the inside out, a new study shows. In an upcoming Science, physicists led by Arjun Yodh of the University of Pennsylvania in Philadelphia describe a model crystal containing water-saturated polymer spheres representing individual atoms.
When heated, the microscopic particles expelled water, shrank, and wiggled freely, and the crystal lost its orderly structure. However, not all of the crystal melted at the same time. Those particles (distorted shapes) surrounding defects within the artificial crystal lattice became disordered at a lower temperature than the other particles did. Yodh says that the new study suggests that the number of imperfections in a material may affect how fast it melts.