First letter is the Bravais symbol describing translational symmetry of the unit cell
(P,A,B,C,R,I,F) followed by a blank (space).
The symmetry operator symbols generating the equipoints in the unit cell follow. They
are all separated by a blank - except if a slash combines them (denoting that the symmetry
plane is perpendicular to the corresponding symmetry axis). Example : I 4/m m m (not case
A screw axis (usually denoted by a subscript following the axis) is entered as two
adjacent numbers :
P 63/M M C, P 21 21 21
An inversion (shown by the bar above the axis) is entered as a minus sign. Example : R
-3 C. The exception is the triade in the cubic systems, which is
automatically recognized as an inversion in the centrosymmetric groups and
thus can be omitted: F D 3 M is ok, and so is F d -3 m.
Settings with origin at center must be used.
Use monoclinic setting with b as unique axis (alpha, gamma = 90.0°).
Use obverse hexagonal setting for rhombohedral space groups.