Hierarchical structures, surface morphology and mechanical elasticity of lamellar crystals dominated by halogen effects

To understand the deformation mechanism of molecular crystals under mechanical forces will accelerate the molecular design and preparation of deformable crystals. Herein, the relationship between structural halogenation and molecular-level stacking, micro/nanoscale surface morphology, and macroscopic mechanical properties are investigated. Elastic crystals of halo-pyrimidinyl carbazoles (CzM-Cl, CzM-Br and CzM-I) with lamellar structure and brittle crystal (CzM-F) were quantitatively analyzed by crystal energy framework (CEF) providing the inter/intralayer interaction energy (Inter/Intra-IE). It is revealed that the elastic crystals bend under external force as a result from stronger Intra-IE to prevent cleavage and weaker Inter-IE for the short-range movement of molecules on the slip plane. This research will provide an insight for the molecular design of flexible crystals and facilitate the development of next-generation smart crystal materials.