Crystal symmetry and Space Groups

DC Levendis 26 March 2010Examples of triclinic crystalsP-1 (space group number 2, 2 general equivalentpositions, 2 molecules per unit cell (i.e. Z=2)•Example: Z=2 for ethyne-nitrobenzene, the moleculeis on a general position). In this case, all of the atomsof the molecule make up one asymmetric unitExamples of triclinic crystalsP-1 (space group number 2)P-1 has 2 general equivalent positions in the unit cell.Example: phenyl-diboronic acid has one ONEmeolecule per unit cell; Z=1:Therefore the molecule must occupy a specialposition. In this case, each general equivalentposition is made up of only half a molecule5