Surface Energy

A surface is an inhomogeneous boundary region betweentwo adjacent phases. As shown in Figure , atoms on the surface of a phase are necessarily different than those in the bulk. In particular, they have fewer nearest neighbors than the bulk, and they may be exposed to constituents from an adjacent phase. This generally means that less energy is required to remove an atom from a surface than to remove it from the bulk. Therefore, the potential energy of surface atoms is higher than bulk atoms. In turn, work is required to move atoms from the bulk to the surface. When this is done, new surface is created, and the surface areaof the phase increases.