EXPAND
: EXPAND archive atom sites 
Authors: Doug du
Boulay
Contact: D. du Boulay,
Materials and Structures Laboratory, Tokyo Institute of
Technology, Nagatsuta, Midori Ku.
The program EXPAND can be used to expand the list
of independent atom sites on the archive bdf (as introduced
using ADDATM) to a complete list of all dependent sites in
the current symmetry defined unit cell, or even multiple
unit cells. This is not a desirable end result of itself,
but it is very useful for converting between different
symmetries and/or unit cell transformations. When followed
by the EXPAND not option, the redundant symmetry related
sites are culled from the archive to restore
normality.
The asymmetric set of atomic sites is read from the
input archive bdf. By default, those sites are expanded to
include all sites in the unit cell. To avoid duplicate name
errors in
ADDATM upd mode the atom
names are amended with cell translation and symmetry
operator strings. This can increase the atom name string
length beyond 8 chars, the standard limit in small molecule
crystallography. Fortunately Xtal handles up to 24
character atom names, so it is not a problem, though not
pleasing aesthetically.
In any case, by following any
EXPAND cell n command
with a matching
EXPAND not, the
extraneous atom name appendages are culled in favour of
simpler, more compact site names.
EXPAND also transforms the anisotropic temperature
factors, but it does not touch the constraint record
lrcons:
, so
it is always necessary to run
ADDATM upd to fix any
broken atom site constraints after running EXPAND.
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