The characteristic features of S-faces (stepped faces, i.e. faces parallel to one periodic bond chain only) are further developed. After giving some definitions, a discussion follows of the factors determining the morphological importance of S-faces. The conclusion is drawn that the development of S-faces in a particular zone can be represented by an addition scheme of indices and that an S-face is the more important, the greater the relative strength of the bonds in the periodic bond chain to which it is parallel.An outline is given of the way in which the morphology of an actual crystal can be derived from the structure. This is illustrated in the case of cubic closest packing. The result is that the octahedron is the most important form, followed by the cube, provided crystallization takes place from the vapour. Crystallization from the melt involves the consideration of pre-condensat~on effects. In this case the influence of the strongest bond on the morphology diminishes and weaker bonds become more important. This leads to a preponderance of the cube, a relation actually observed with copper.

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Elucidation of the structure of a new sodium superionic conductor, Na11Sn2PS12via single crystal XRD and AIMD simulations reveal isotropic 3D Na+-ion conduction pathways.

The morphology of barite is deduced from the structure. It is found that there are six F-forms, namely {001}, {010}, {211}, {210}, {101} and {100}. An estimate of the relative importance of these faces is obtabmd by approximate calctflations of the attachment energies. The results are in satisfactory agreement with observations.The form {011 } is found to be a K-face. Its relatively high morphological importance is explained in terms of dehydration and impurity effects.All other forms of some importance appear to be S-forms. Crystals of some compounds isotype with barite, grown from pure aqueous solutions, show only the six F-forms, and {011} due to the dehydration effect. This suggests the assumption that the occurrence of S-and K-forms on minerals is due to a period of dissolution followed by growth in an impure environment.