```6.3.5.1.  SETTING LINKS/BONDS BETWEEN ATOMS

Option [C] selected from the graphics option menu G, see Sec. 6.3.5, allows
you to define links connecting atom pairs and shown in plots by straight
lines or cylindrical sticks. This can be used to visualize chemical bonds or

== GRAPHICS OPTIONS ===================================================
1)    nuc1  nuc2     rmin       rmax     lcol        lrad
2)  ...

[N]ew [A]dd [E]rase [C]olrs [R]adii c[T]abl [D]ispla {[X]plot} [?,]esc
================================================================= 32 ==

where nl is the number of link constraints defined at present. Each
constraint is given by one line where two different types can appear:

For positive nuc1 and nuc2 the values refer to nuclear charges (values
nuc1/2 = 0 are meaningful, see below) and are followed by a distance
range [rmin, rmax], a line/stick color lcol, and a stick radius lrad.
Here a link constraint means that any two atoms of the cluster will be
connected by a line or cylindrical stick if one atom is of nuclear
charge nuc1, the other of charge nuc2, and if the distance between the
two atoms lies inside the distance range [rmin, rmax].

For negative nuc1 and nuc2 the values refer to atom numbers. The distances
rmin, rmax are meaningless and set to zero while the line/stick color
that only the two cluster atoms of numbers -nuc1 and -nuc2 will be
connected by a line or cylindrical stick.

For stick radii rad = 0 atom pairs will be connected by thin lines of color
and of color lcol . With atoms shown as (shaded) balls lines/sticks will
connect ball surfaces thus enhancing the 3-dimensional impression.

Charge values nuc1/2 = 0 ignore the respective charge constraint. Thus,
nuc1 = nuc2 = 0 connects any pair of atoms with a distance inside the
prescribed range while for example nuc1 = 14, nuc2 = 0 connects all Si atoms
with any other cluster atom A if the Si-A distance lies inside the distance
range [rmin, rmax].

All options of the link option menu GC are identical to those of the