Change here the reference object data for a single group only.
To modify a group, click over its graphic image, or write its identification
(name and number) on the
Group entry. To modify a list of groups,
press the button
List (after creating the list of groups with
Group->Select). Parameters for empty entries or
Local
choices remain unchanged.
To change a group name write the new name in the
Group entry,
followed by the group number (GAMGI needs the number to identify the group).
To change the name for a list of groups, press
List first
and then write the new common name in the
Name entry.
Reference
GAMGI can handle groups that are just object containers (selecting
Container), and coordination polyhedra, requiring a central
atom (selecting
Polytope).
For a single group,
Reference can be
Container,
Polytope
or
Local. For a list of groups ,
Reference must be
Local.
When
Container or
Polytope is selected, the group
is recreated from scratch (as if using
Group->Create) and its
old content is removed. As this requires local information for each group,
it cannot be done for a lists of groups. When
Local is selected,
previous features and contents are preserved, unless when specifically changed.
Container
The primary purpose of a group container is to contain other objects.
When a group container is created, it has no child objects and consequently
no visual representation. The only way to select an empty group is
thus to write its identification or to use the mechanisms provided
by
Group->Select.
To avoid this problem, when
Ok is pressed and the new group is
created, the dialog
Group->Create is automatically replaced by
Group->Link, with the new group identification already inscribed
on it. How to link objects to a group is described in the section
Group Link.
Polytope
For an arbitrary cloud of atoms, defined by
Central and
Neighbours settings, build a coordination polyhedron defined
by the smallest convex polygonal representation that surrounds all
the atoms. This is often used in Crystallography to build tetrahedra,
octahedra, and other small regular solids, but the method can be used
to build polyhedra for an arbitrary set of atoms, independently of
their position or number.
When Gamgi cannot build a 3D polyhedron, automatically tries to build
a 2D atomic plane, as in
Plane->Create. When a 2D plane cannot
be defined, automatically tries to build a 1D atomic direction, as in
Direction->Create. When a 1D direction cannot be defined, an
error is shown.
Central
Enter here the name and number of the central atom, around which the
coordination polyhedron will be built. Pressing the mouse over an atom
in the current layer, the atom identification is automatically written
in the
Central entry.
When
Local is selected (the default), only one polyhedron is
constructed, around the
Central atom. When
Global is
set, Gamgi builds coordination polyhedra around all the atoms in
the sampling universe with the same element as the
Central
atom.