Lattice imaging of radiation-sensitive materials

Two examples of the application of lattice imaging of molecular crystals are given. The first is the study of the β to α phase change in copper phthalocynamine brought about by crushing to pigmentary size particles. The second is the study of crystal behaviour and structure determination of the aromatic hydrocarbon series coronene, ovalene and hexa benzo coronene. The advantages of lattice imaging are, improved resolution with respect to radiation damage and secondly, the specimen does not require specific orientation. The copper phthalocynamine showed the application of phase identification from which the phase transformation could be studied. Lattice images of the hydrocarbons showed that molecular rows either bend at junctions to minimise strain energy or have a rigid angle which comprises a regular stacking sequence avoiding strain energy from mismatch. (U.K.)