Electron crystallography of the polymethylene chain. 5. Three-dimensional structure of a Fischer-Tropsch wax

The crystal structure of a Fischer-Tropsch wax, Shell Callista 158, has been determined in three dimensions from electron diffraction intensity data. Although there is an orthorhombic layer arrangement with apparent dimensions, a = 7.42, b = 4.96, c = 94.50 Angstrom, true lamellae cannot form, due to a 'nematocrystalline' arrangement of very long chain components, generating a continuous chain direction through adjacent chain layer clusters. The structure is actually a superlattice of the Pnam cell observed for high molecular weight polyethylene.