Crystal surfaces and crystal growth mechanisms: Application to crystals having the NaCl structure and especially silver halide crystals

Results of computer simulation studies of crystal surfaces and related crys tal growth mechanisms as well as statistical mechanical roughening transiti on theories of these surfaces are reviewed. The implications of these theor ies for crystal growth mechanisms. such as the spiral growth mechanism and the substep mechanism, recently described by Ming and co-workers, are treat ed briefly. Relations between roughening theories and recent developments i n the crystallographic morphological theory of Hartman and Perdok are intro duced. It is shown how this integrated theory can be applied to crystals ha ving an NaCl structure., such as AgBr and AgCl crystals. The most stable fa ces are the {100} and {111}, faces respectively. The {111} faces will be st able only if the high dipole moment can be removed by reconstruction or int eraction with the solvent. Supersaturation is the key parameter that determ ines the growth morphology. At low supersaturations, only {100} faces are p resent. At higher supersaturations, {111} faces will become dominant. On th ese faces, formation of twins will occur at even higher supersaturations. l eading, as a result of the substep mechanism, to tabular and needle-like cr ystals. The detailed understanding of all kinds of tabular and needle-like AgBr and AgCl crystals will be the subject of a subsequent paper.