The unit cell is monoclinic, space
group P21/c, with the cell parameters shown in the upper-left corner of the Java frame.
At this point, the cell contains one molecule; this is the so-called asymmetric unit. The other three molecules in the cell will be related to this one by the space group symmetry. The origin of the unit cell is near this asymmetric unit molecule (there is a red "dot" at the origin of the unit cell). It is helpful to orient the cell so the view is down the b-axis (the b-axis is the cell axis that is perpendicular to the two other cell axes). To rotate the cell move the cursor inside the java frame while holding down the (left) mouse button. A 2-fold screw axis parallel to b at x=0, z=1/4 produces a second molecule at -x, 1/2+y, 1/2-z: A center-of symmetry at the origin of the cell, produces a third molecule at -x, -y, -z: A c-glide perpendicular to b at y=1/4 produces the fourth molecule at x, 1/2-y, 1/2+z: |