This sample corresponds to a school case. Synchrotron data were collected at Daresbury (wavelength 1.52904 A). Cimetidine is in the PDF-2 (two cards). The search by EVA-2 limited to organic data is successfull (cim1.gif). With such high quality data, it could be sufficient to get the reflection positions as corresponding to peak maxima. The three stars or indexation give the same result . As expected from synchrotron, the FOM (figure of merit) are quite brilliant : M(20) = 100 and F(20) = 248.(0.0032, 25) from TREOR90 results without searching for any zeropoint (the FOM are even better with a zeropoint = -0.008° 2-theta added to the observed positions, this zeropoint value being that refined at the last stage by the Rietveld method).
The cell is monoclinic. Applying the Le Bail method for cell confirmation, a quite good fit is obtained with the P2/m space group selected for a further hunting of possible systematic extinctions (in order to be consistent with the original already published work, the cell will be later considered in the non-standard setting P21/n space group).
Try by yourself, downloading the full data (cim0.zip).