This is the only centrosymmetric orthorhombic point group. Note that the symbol mmm is a shortened form of the full symbol 2/m2/m2/m. The figure above shows the three mutually-orthogonal mirror planes plus the three mutually-orthogonal twofold rotation axes present in this point group. The white circle in the centre of the figure indicates the centre of inversion.
(You may like to compare this figure to the symmetry of C2O4= shown earlier.)
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| © Copyright 1997-2006. Birkbeck College, University of London. | Author(s): Jeremy Karl Cockcroft |