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The correct form for the symmetry code is described below. The most common error
is the use of symmetry codes such as those used in PLATON (of the form 54502).
The symmetry code of each atom site as the symmetry-equivalent
position number 'n' and the cell translation number 'klm'.
These numbers are combined to form the code 'n klm' or n_klm.
The character string n_klm is composed as follows:
n refers to the symmetry operation that is applied to the
coordinates stored in _atom_site_fract_x, _atom_site_fract_y
and _atom_site_fract_z. It must match a number given in
_space_group_symop_id.
k, l and m refer to the translations that are subsequently
applied to the symmetry-transformed coordinates to generate
the atom used in calculating the bond. These translations
(x,y,z) are related to (k,l,m) by the relations
k = 5 + x
l = 5 + y
m = 5 + z
By adding 5 to the translations, the use of negative numbers
is avoided.
Examples:
| .
| no symmetry or translation to site
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| 4
| 4th symmetry operation applied
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| 7_645
| 7th symm. posn.; +a on x; -b on y
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