Detecting Crystalline Nonequilibrium Phases on the Nanometer Scale

The use of Automated electron Diffraction Tomography (ADT) is presented as a novel approach for crystallization studies at the nanometer scale for nonequilibrium phases. Here, ADT was applied to elucidate the structural identity of the recently reported hexagonal morphology of caffeine crystals, which grow only on specific surfaces. Caffeine was crystallized from solution on a specially treated TEM carbon grid. The analysis of ADT data revealed that the lattice parameters of these hexagons match those of the high temperature α- form of caffeine. Furthermore, it was observed that in this hexagonal morphology, the α-form remained stable for a prolonged period of time. The stabilization of hex…