The Institute of Pharmaceutical Innovation

Study of the effect of solvent on the morphology of crystals using molecular simulation

Study of the effect of solvent on the morphology of crystals using molecular similation

S. Khoshkhoo & J. Anwar*

The interaction of water as a solvent on selected faces of crystals of N-n-octyl-D-gluconamide and alpha-resorcinol has been examined using the Monte Carlo molecular simulation technique. The interaction energies for N-n-octyl-D-gluconamide are in good agreement with the experimentally observed contact angles, and indicate that a favourable interaction between the solvent and a crystal face is consistent with observed slow growth. For alpha-resorcinol, the interaction energies for the two faces studied are similar even though one of the faces is known to grow considerably faster in water than the other. Examination of the structural features revealed that at the (011) interface (the slow-growing face) the water is incorporated into pocket-like grooves. This suggests that the low growth rate of the (011) face is due to the strong and specific interactions of water at these pockets rather than a general non-specific interaction. These simulations indicate that in predicting the effect of solvent on the morphology, one needs to consider not only the non-specific interaction of the solvent with the face but also any possible specific interactions.