Dialog Box: Epitaxial Crystals [ Input1 Menu]
This option allows many complicated intergrowths of different crystals, as well as off-center twins, to be drawn. In epitaxial intergrowths, in principle a face of one crystal lies on a face of another crystal, either of the same or a different species. The mutual orientation must be further specified by the vectors within the faces which are parallel. Although the mutual orientation is described in terms of the faces, the crystals may after a period of growth be interpenetrating, or one may partially or completely enclose the other. In practice the "face-on-face" relation may only specify the mutual orientation, not position, and this option can be used to draw crystals with almost any kind of relation.
There are four ways to generate an epitaxial guest crystal: you can Duplicate the selected crystal; you can Add a new crystal with manual entry of the symmetry and forms; you can Read from File (that is from a .SHP data file); or you can Import an external file.
If you choose the Read from File option, the file in question must have been saved by SHAPE for Windows or in the ASCII "exchange" format with SHAPE for DOS V4.2. If you duplicate or read from a file, you will be transferred immediately to the Epitaxial Relations dialog.
To Import an epitaxial crystal, go directly to the Import option in the File menu (instead of this dialog). When the file has been read, you will be transferred immediately to the Epitaxial Relations dialog.
The host crystal is always crystal number 1; thus epitaxial guest crystals are always numbered from 2 upwards.
Orientation of crystals through epitaxial relationships involves a series of complex operations and is inherently less precise than orientation with twin operations. Occasionally, errors in drawing may result from this lack of precision. Twin operations should be used instead of epitaxy whenever possible to generate intergrowths.
Intercrystal edges are located only once during the calculation, after all crystals have been oriented and translated. If there are any crystal which actually do interpenetrate with one another, this box should be checked. If all epitaxial crystals are of the contact variety, it may be unchecked.