Patterson function of plagioclase satellites

The real and imaginary parts of Patterson functions based on `e' and `f' satellites were calculated. In `e' satellite maps, Patterson interactions involving cations are most prominent and permit relatively simple calculation of the amplitudes and phases of 26 displacement modulation waves. The deformation of the silicate chain, which is apparently one of the major features of the plagioclase superstructure, is shown in detail. The interpretation of the `f' satellite Patterson function is less straightforward, but it shows clearly that the associated displacements are of very small amplitude, directed along [02] and that they do not involve Na/Ca cations.