Growth and lattice defects of hexamethylbenzene crystals

Single crystals of hexamethylbenzene, C-6(CH3)(6), were grown from benzene or xylene solutions. The various crystal shapes such as plates, ribbons, whiskers and rhombohedral blocks were observed, the prism planes were (100), (010), (001) and (110). The ribbons and plates have well developed (100) or (001) planes and grew along the (010) axis. Twinned crystals were also observed; the composition plane and the twin boundary is (001). Lattice defects of the crystals were investigated by X-ray topography. Dislocations with Burgers vectors [100], [010] and [<(1)over bar 10>] were observed. The slip plane was (001). Dislocations with the shortest Burgers vector, [001], were not observed. The specific features of dislocations in hexamethylbenzene crystals are discussed in terms of the steric hindrance of molecules to slip.