What does M mean in space group?

mirror plane perpendicular
The space group of hexagonal H2O ice is P63/mmc. The first m indicates the mirror plane perpendicular to the c-axis (a), the second m indicates the mirror planes parallel to the c-axis (b), and the c indicates the glide planes (b) and (c).

What is C2 m space group?

The three space groups C2/m, C2 and Cm have the same systematic forbidden reflections which are caused by the C-centering (h+k = 2n+1). The other symmetry operations in the three space groups, e.g. 2-fold rotation axis (2) and mirror plane (m) in the C2/m space group, do not cause forbidden reflections.

What do space group symbols mean?

The symbols of the cubic space group symbols refer to the lattice type (P, F, or I) followed by symmetry with respect to the x, y, and z axes, then the threefold symmetry of the body diagonals, followed lastly by any symmetry with respect to the face diagonals if present.

How do you calculate space group?

Space group determination entails the following steps: determine the Laue class: this is the symmetry of the intensity-weighted point lattice (diffraction pattern). 1,2,3,4,6=n-fold rotation axis; -n means inversion centre (normally the – is written over the n); m means mirror.

What is 2m point group?

2/m: Point group 2/m has a 2-fold axis of rotation perpendicular to a mirror plane. Technically it’s more accurate to say the axis of rotation is “parallel to the normal” of the mirror plane, because the “/” sign indicates parallel elements, and mirror planes are defined by their perpendicular vector.

What is meant by space group?

space group, in crystallography, any of the ways in which the orientation of a crystal can be changed without seeming to change the position of its atoms.

How many space groups are there?

There are 230 space groups in three dimensions, given by a number index, and a full name in Hermann–Mauguin notation, and a short name (international short symbol). The long names are given with spaces for readability.

What is 2m symmetry?

Tetragonal-scalenohedral Class, 2m, Symmetry Content – 1 4, 2A2, 2m. This class has a 4-fold rotoinversion axis that is perpendicular to 2 2-fold rotation axes. The 2 mirror planes a parallel to the and are at 45o to the 2-fold axes. Chalcopyrite and stannite are the only common minerals with crystals in this class.

What is 2mm symmetry?

A motif with 2mm symmetry. This Class (2mm) can be based on several different internal structures, which means that more than one Plane Group is possible to support it. Such a Plane Group represents the total symmetry content (point symmetry as well as translational symmetry) of the pattern of repeated motifs.