Evaporation of Metal Crystals

A mechanism for vaporization of solid metals involving monatomic ledges on metal crystal surfaces is deduced, and an equation is derived for evaporation rate in terns of the dynamics of these ledges. It is shown that crystal edges are a ready source for monatomic ledges. The limiting expression for the vaporization coefficient of large, perfect crystals is given as a function of pressure and temperature by α = 2/3 (p/p_e ) ≠ 1/3, where p_e is the equilibrium vapor pressure. The effect of screw dislocation-surface intersections on the limiting expression is developed. An equation is derived giving the perturbation due to such intersections. It is found that experimental results for silver crystals confirm various predictions of the theory. Applications of the results are considered.