Interpretation of the pair function for laminar amorphous materials in the case of coals. II. Structure of coals

From studies on six petrographic components of Polish coals by the radial distribution function method and the interatomic distances calculated from them the proportions of atoms with sp² and sp³ hybridization and the extent of units with sp³-type structure were determined. From these data and the results of the pair-function analysis performed in paper I [Grigoriew (1988). J. Appl. Cryst. 21, 97-101], the model interpretation of the structure of these materials was carried out by matching experimental and model pair functions P(r). The model was defined as an average structural unit which scatters X-rays coherently. It appears that such units in these materials are larger than previously expected and for vitrinites and fuzinites they are in the form of turbostratic layers. The process of formation of stacks of layers was observed in components with the lowest degree of ordering.