Surface energy

Work must be done to cut a crystal into two pieces that expose a pair of new crystal faces or facets. The energy required to bring about this cleavage, called the surface energy, is proportional to the density of the various types of chemical bonds that are cut and transformed into dangling bonds. In the case of fcc crystals, each large atom has 12 large atom nearest neighbours to which it can be bonded. Each medium sized atom in an octahedral site is bonded to six surrounding large atoms, and each small atom in a tetrahedral site is bonded to four large atoms. Which bonds break depends on the particular crystallographic plane where the cleavage occurs.


Owens et al,2008, The physics and chemistry of Nanosolids, Wiley, p 17