Settings and Systematic Absences

There are other things to note on this sheet. Up near the center, there's the statement that the origin is on an inversion center and the unique axis is b. This is redundant with "2ND SETTING".

And then there's the right-hand column of things. These have to do with systematic absences. We'll get to them later in more detail, but for now you should simply know that some symmetry elements give rise to zero intensities for particular reflections. So if you see a set of systematic absences in the diffraction pattern, you can work back to identify the space group or at least limit the choices to a few space groups.

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copyright © Ron Stenkamp stenkamp@u.washington.edu Most recent update 1/17/97