GROWTH HABIT AND SURFACE-MORPHOLOGY OF L-ARGININE PHOSPHATE MONOHYDRATE SINGLE-CRYSTALS

The results of a study of the growth habit and the surface topography of L-arginine phosphate monohydrate (LAP) single crystals as a functio n of supersaturation are described and discussed. Apart from a change in the growth habit with supersaturation, it was observed that most of the as-grown faces of LAP exhibit isolated growth hillocks and macroh illocks and parallel bunched layers and that the formation of bunched layers is pronounced on faces showing macrohillocks. Observations of b unching of growth layers emitted by macrohillocks on the {100} faces r evealed that, for the onset of bunching close to a macrospiral, there is a characteristic threshold distance whose value depends on the inte rstep distance and supersaturation, but is independent of step height. The theoretical habit of LAP deduced from PBC analysis showed that al l faces exhibiting growth hillocks and macrohillocks are F faces. Anal ysis of the results on bunch formation revealed that growth of LAP tak es place by the direct integration of growth entities at the growth st eps, that the bunching is facilitated by an increasing value of the ac tivation energy for their integration, and that the observed dependenc ies of threshold distance on interstep distance, supersaturation and s tep height are qualitatively in agreement with van der Eerden and Mull er-Krumbhaar's theory of bunch formation.