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**All of the space group diagrams are drawn with the origin placed at
the bottom left-hand corner of the diagram.**

For the triclinic and monoclinic space group diagrams, the use of prime (') on the labels for the cell lengths (or angles) indicates that the length (or angle) is seen in projection on the XY plane of the screen. Similarly, the same comment applies to projections seen down the body-diagonal of the primitive rhombohedral unit cell.

For the orthorhombic space groups nos. 73 and 74, two-one axes are used
in the long form of the space group symbols in order
to emphasise the relationship of these space groups to
*P*2_{1}2_{1}2_{1}.

For many of the *C*- and *F*-centred tetragonal space groups,
only a single quadrant has been drawn due to space limitations.

Only primitive unit cells have been drawn for the hexagonal space groups
in contrast to the trigonal space groups where the *H*-centred cells
are also shown.

For the cubic space groups, the diagrams show only the symmetry elements
and not the symmetry equivalent positions of a point in an asymmetric
position within the unit cell.
Due to the limitations imposed by both space and resolution,
for space groups nos. 203, 209-10,
216, 219-20, 225-8, and 230 only one quadrant of the unit cell is drawn.
(For the *F*-centred unit cells, a single quadrant suffices since each
quadrant appears the same in projection.)
Due to the same limitation, the -4 axes are not shown for space groups
nos. 225-6, and 229.

© Copyright 1997-1999. Birkbeck College, University of London.