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Cameron Manual
Chapter 18: Add And Move - Further Symmetry Related Commands
The PACK and ENCLOSURE commands already detailed allow the user to apply all of the symmetry operators in the spacegroup to the initial set of atoms in order to get a fully 'packed' result. In some cases however, the user may wish to apply only one symmetry operator or to apply ones that are not present in the spacegroup. The ADD and MOVE commands allow this.
[Top] [Index] Manuals generated on Wednesday 8 November 2006
18.1: ADD
The ADD command allows the user complete control over the symmetry operator used to generate new atoms. The first task of the user is to generate a list of those atoms to be used in the symmetry generation later. One of the following sub-commands is required :-
The names of atoms to be included in the pack list are specified here. Element names can also be used if required.
ALL refers to the atoms that are in the current list. If any atoms have been generated by previous PACK , ENCLOSURE or ADD commands then these will all go into the list.
ADD INITIAL means that the only atoms to go into the ADD list are those that were initially input.
This is followed by a group name. The group must have been previously been defined by the command DEFGROUP.
Once the ADD list has been created the user must then supply the symmetry operators which will act on the atoms in this list to generate the new atoms. The symmetry input is in two parts.
x y+1/2 z -0.333-x -y -z ETC
Decimal translations may come before or after the axis symbol.
The fractions 1/2, 1/3, 1/4, 2/3, 1/6 and 5/6 are accepted by the
program, but must appear after the
x/y/z
character. There must be spaces between the three parts but NO
SPACES
within the operator ie
X + 1/2 -Y Z
will produce an error as it is not possible to tell whether you
mean
X+1/2, -Y, Z or X, +1/2-Y, Z. This strict input syntax is used
to eliminate
any ambiguities.
TRANS x y z
[Top] [Index] Manuals generated on Wednesday 8 November 2006
18.2: EXAMPLES
ADD ATOMS C1 OPERATOR X+1/2 Y Z
or we could use
ADD ATOMS C1 TRANS 0.5 0 0
The OPERATOR and TRANS commands can be used together if required.
We can
apply a symmetry operator followed by a translation. This reduces
the
errors that may occur when trying to combine the two things into
one
symmetry operator.
The use of INITIAL versus ALL is illustrated below. Start with
:-
ADD ALL TRANS 1 0 0
which gives us a molecule at x y z and another at x+1 y z.
Follow this with :-
ADD ALL TRANS 0 1 0
and we get four molecules, x y z , x+1 y z , x+1 y+1 z and x y+1
z.
Following it with :-
ADD INITIAL TRANS 0 1 0
Gives us three molecules, x y z, x+1 y z and x y+1 z.
[Top] [Index] Manuals generated on Wednesday 8 November 2006
18.3: MOVE
The syntax for this command is identical to that for ADD. Therefore the commands available are :-
Which must be followed one (or both) of :-
The MOVE command applies a symmetry operator and/or a
translation to
all of the atoms held in the list defined by the
ATOMS/ALL/GROUP/INITIAL
commands. Unlike ADD therefore, the same number of atoms are
present at
the beginning and end of the operation.
[Introduction | How To Get Started | Data Input | Outputting Data | Editing The Atom List | Obeying Files | Archiving And Retrieving Views | Graphical Output Devices | View Direction Control | Include And Exclude | Drawing Style Control | Connectivity Control | Control Of Colour | Atom Labelling | Other Picture Controlling Commands | Symmetry Input | Crystal Packing Commands | Add And Move - Further Symmetry Related Commands | Distance And Angle Calculations | Information On Data Held Within The Program | Group Definitions | Miscellaneous Commands | How To Stop The Program | Menu Definition File | Some Useful Ideas ]
