Simulation of energetic stability of facetted l-glutamic acid nanocrystalline clusters in relation to their polymorphic phase stability as a function of crystal size.

A molecular modeling approach is used to study the stability of different polymorphic forms of l-glutamic acid through building and optimizing molecular clusters of different sizes and shapes with the latter corresponding to the predicted crystal growth morphologies. The results reveal that the initially nucleating (according to Oswald rule) metastable (alpha) form is the more energetically stable form at small cluster sizes of ca. 200 molecular units, whereas the stable (beta) form is more stable when the cluster size is larger.