Add/Revise Form
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Dialog Box: Add/Revise Form [ Forms List Dialog ]

<Standard Mode - see also Add/Revise Form (Cartesian)>

The central distance is the perpendicular distance from the center of the crystal to the faces of the form in question: the greater the distance, the smaller the area of the face (calculated areas are printed in the List Results option in the File menu). Also, if there are many forms, the greater the distance the less prominent the form (the smaller the area of the faces). Decimal values may be used for the central distance, but not for the indices. Use the Next Form button to add a form.

You can use negative central distances to define a crystal which does not lie on the origin; see the rutile twin example in Chapter 5 of the Instructions.

For hexagonal and trigonal crystals with hexagonal axes, four indices, (hkil), are commmonly used, but one of the first three is redundant. In SHAPE, you must omit the third, or i index.

The Form letter may be used to label each face in the conventional way. Whether numerical indices, form letters or no labels at all are shown is set in the Labels dialog in the Display menu.

The color, b/w pattern and pen number are used primarily for sections and growth zones and may be used for form fills.

The Rate Constants button pertains to growth zones. It brings up either the Exponential Growth-Rate Constants dialog or the Growth Intervals dialog, depending on the Exponential/Discontinuous setting in the Growth Zone Settings dialog. The rate parameters can also be set from the latter dialog.

See the Forms List dialog for the addition of imaginary faces, edges and corners if the real faces do not define a closed shape.