Asymmetric Growth of α-Resorcinol Crystals: In Situ Studies of Crystal Growth from the Vapor Phase

Abstract

In situ studies of the growth of the acentric crystal α-resorcinol from the vapor phase confirm that the mechanism of growth differs on the faces presented at the opposite ends of the polar axis of this material. At medium supersaturations (σ = 0.76), the growth of the (01̅1̅) and (011̅) faces proceeds by the cooperative development of strongly propagating growth sources. Under similar conditions, the (011) and (01̅1) faces develop a mosaic of flat-topped growth centers. These develop individually and merge to form a continuous, curved, facet bearing a few residual, weakly propagating birth and spread growth sources. The degree to which this mosaic growth occurs depends on the damage done to the face of the seed crystal during preparation. This behavior accounts for the previously observed wide variation in the estimates of growth rate of the positive faces and the differential in growth rates compared with that of the negative faces. On more perfect (011) surfaces, growth is restricted to a small degree of nucleation at isolated random centers. These nuclei undergo a more limited localized growth to yield a nonpropagating macroscopic surface roughness. These observations provide further evidence for our previously expressed contention that the anisotropic growth of this and related highly polar acentric materials arises from intrinsic mechanistic causes.