Distribution of molecular centres in unit cells with respect to packing patterns.
Packing patterns, a new description of the limited number of possible arrangements of molecular building blocks in a unit cell, were assigned to many thousands of structures belonging to the space groups P2(1)/c, P1(-), P2(1)2(1)2(1), P2(1) and C2/c. The position of the molecular centre (in fractional coordinates) in the unit cell for these structures has been surveyed, with respect to the space group and the packing pattern. The results clearly show that the position at which the molecular centre is found in the unit cell is correlated with the packing pattern. The relationships between the orientation of the packing pattern in the unit cell and the symmetry operators of the space group are explored. Popular orientations of packing patterns within the unit cell are given.
Pidcock
Elna
E
Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, England. pidcock@ccdc.cam.ac.uk
Motherwell
W D Sam
WD