Facet stability of crystals I. Factors determining the polyhedral (in)-stability of silver single crystals during electrocrystallization at high current densities

Abstract

Loss of the polyhedral stability as a result of emerging depressions on crystal faces has been observed during both vapour and solution growth under diffusion control, as well as by electrocrystallization at high current densities. A difference was found only when a quantitative comparison of the stability of the crystal shapes with the existing theoretical predictions was attempted. With the growth of zinc and cadmium single crystals from the vapour phase this phenomenon appears earlier, i.e. at smaller sizes than the expected figures, while the silver single crystals are more steady — they withstand one order of magnitude higher of current densities than the calculated values before the appearance of the depressions, in spite of the fact that the presence of an (inhomogeneous) electrical field in the second case has to decrease the polyhedral stability. One possible explanation of this fact is that the electrocrystallization of silver proceeds in highly concentrated solutions, for which Seeger's equation, laying in the base of the quantitative elucidations in this case, does not hold true. Correspondingly, here (part I of the paper) we are trying a more general approach, while part II represents a new, alternative way for explaining the higher stability of the faceted forms of the silver single crystals.