Kink Rate Model for the General Case of Organic Molecular Crystals

Abstract

Recently, a general mechanistic spiral growth model, including a kink rate expression that enables crystal morphology prediction for all kinds of organic molecules (both centric and noncentric), was developed. However, we have discovered that the kink rate model for the step velocity in solution growth is inconsistent with the attachment and detachment rate expressions for noncentric growth units at kink sites, so these expressions are revisited to make them self-consistent. Here, we derive a new expression for the kink rate for noncentrosymmetric organic molecules, which correctly accounts for the effect of solvent molecules on growth kinetics. We also generalize the kink rate model to consider other species such as additives. Using the spiral growth model with the improved kink rate expression, we have studied the steady state morphology of paracetamol crystals at low supersaturation to understand the morphology transition induced by the solvent effect and compared our predictions with experimental meas...