Hello, Raja!
The space group Pnma is centrosymmetric, since it belongs to the mmm class . Here is a link to a complete list for all space groups and their symmetries.
regards,
Daniel
http://pd.chem.ucl.ac.uk/pdnn/symm3/allsgp.htm
Hello, Raja!
The space group Pnma is centrosymmetric, since it belongs to the mmm class . Here is a link to a complete list for all space groups and their symmetries.
regards,
Daniel
http://pd.chem.ucl.ac.uk/pdnn/symm3/allsgp.htm
Hello
You have a fantastic server to obtain a lot of information about symmetries and other things. Please visit it.
Bilbao Crystallographic Server http://www.cryst.ehu.es
Dear Raja,
there are general rules to obtain a center of symmetry in Crystallography:
i) A crystal is center-symmetric if its morphological symmetry has only one symmetry element , i.e. an "inversion center"; this is the case for the pinacoidal class of the triclinic system
ii) Another possibility is for the monoclinic, in the class 2/m, where a rotation axis A2 is perpendicular to a symmetry plane (m); also in this case every point of coordinates (x,y,z) is reproduced in another one of coordinates (-x, -y, -z).
iii) Finally you have many other possibilities, in the higher symmetry systems. It is sufficient that a rotation axis ( A2 or A3 or A4 or A6) is perpendicular to a mirror plane and, consequently, an inversion center will be obtained.
Then, your Space Group, has 3 mirror planes, mutually perpendicular each other (as it happens in the orthorhombic system. Thus, three axes A2 are generated at the intersection of two planes and then they are perpendicular to the planes. So an inversion center is obtained.
All the best !
Dino
- Badges
- Science method
- Similar topics
- Methodology
- Crystallography