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Dialog Box: Forms List [ Input1 Menu] [ Epitaxial Crystals Dialog]

This lists the forms for the current crystal - this is the main crystal if this dialog is called from the Input1 menu, or an epitaxial crystal if called from the Epitaxial Crystals Dialog.

Multiply central distances by factor. Most calculations in SHAPE depend on finite tolerances to decide whether corners are not outside of any face, whether a corner derived from one triplet of faces is coincident with another, etc. Sometimes there are errors, for example extra corners, missing edges, or missing faces ( in the Shading or Face Fill options, or in 3D mode). See Precision, Tolerances... for more details. In many cases such errors can be eliminated by changing all central distances by the same factor, which effectively changes the relative tolerances. An increase in central distance is most likely to help, although a decrease may be required in some cases. If the Multiply all parameters by factor box is checked, parameters which involve absolute central distance units will be multiplied by the factor. Such parameters include fixed scale factors (Scaling); Perspective distance; Striation spacing; fixed Displacements of the crystal; Crystal Axes and Labels; Growth Rate and time parameters; and sizes of cylindrical edges and symmetry elements in the 3D modes (3D Parameters)

Clicking on the Add or Revise buttons calls up the Add/Revise Form dialog (Standard or Cartesian).

When called from the Input1 menu, this dialog can only modify the main or host crystal of an epitaxial intergrowth. Epitaxial guest crystals are modified from the Epitaxial Relations dialog.

Imaginary faces, edges and corners . The user is responsible for specifying enough forms to make a complete crystal. After having generated all symmetry-equivalent faces and computing corners and edges, SHAPE applies some simple tests to see if a closed shape has been defined. If a closed shape does not seem to have been defined, you have the option of computing again to define imaginary edges and corners. This is done by adding "imaginary" faces at a central distance just greater than the most distant real corner, or about 1.5 times the largest central distance if no corners have been found. These faces are those of the unit cell, except for trigonal and hexagonal crystals, which use a trigonal or hexagonal prism. The edges which terminate the real faces against these imaginary faces are drawn with a different color (see Line Colors) and in the printed output (List Results dialog, File menu) these edges and associated corners are marked as Imaginary. These imaginary edges are not visible from the back side of the real faces unless Back edges are selected in the Line Attributes dialog (Input2 menu).

For the Cartesian or QSHAPE mode of operation, the imaginary faces are (100), (-100), (010), (0-10), (001), (00-1) and all their symmetry equivalents. This may lead to a very large number of faces and correspondingly long calculation times.