The Effect of Surface Molecular Conformational Change on Morphology: A Study of Benzil (0001)

Why Are Some Crystals Straight?

“…Roberts and co-workers surmised that the differences between the gas-phase and ground-state conformation of benzophenone and its crystal structure conformation could account for the unexpected morphologies of solution-grown crystals via reconfiguration of surface molecules . Later, he and others showed by simulation, with support from X-ray absorption near edge structure (XANES) spectroscopy, that the molecules on the {0001} surfaces of benzil were distorted from their crystal conformations. , In fact, these computations suggested to us the possibility of testing surface stresses as a cause of crystal twisting and directed us to our emphasis on benzil here, among the innumerable other sometimes twisted crystals we might have selected. However, we did not observe comparable changes in conformation at benzil {0001} surfaces with the GAFF or CVFF force fields under geometry optimization or molecular dynamics simulation.…”

“…61 Later, he and others showed by simulation, with support from X-ray absorption near edge structure (XANES) spectroscopy, that the molecules on the {0001} surfaces of benzil were distorted from their crystal conformations. 62,63 In fact, these computations suggested to us the possibility of testing surface stresses as a cause of crystal twisting and directed us to our emphasis on benzil here, among the innumerable other sometimes twisted crystals we might have selected. However, we did not observe comparable changes in conformation at benzil {0001} surfaces with the GAFF or CVFF force fields under geometry optimization or molecular dynamics simulation.…”

Surface Reconstructions in Organic Crystals: Simulations of the Effect of Temperature and Defectivity on Bulk and (001) Surfaces of 2,2′:6′,2″-Ternaphthalene

“…Despite these characteristics, judging from the scientific literature, molecular crystals usually undergo very small relaxation with respect to the bulk. While for inorganic surfaces a rich literature and a surface structure database are available, reports on surface reconstructions of molecular solids are sparse. − We are aware of only a few examples concerning pyrene (001), benzyl (001), , and benzophenone surfaces, while recent molecular mechanics minimizations (i.e., excluding thermal disorder) on organic semiconductors crystals exhibiting the typical herringbone packing showed that surface relaxation of the low energy crystal faces is in general negligible. − The recent study of Morisaki et al, conversely, has shown that surface relaxation in tetracene single crystals may have a deep impact on electron transport properties.…”