<div dir="ltr">Dear CCTBX-list<div><br></div><div>I am trying to reproduce the (scaled) intensities for Si reported here: <a href="http://rruff.geo.arizona.edu/AMS/xtal_data/DIFfiles/15285.txt">http://rruff.geo.arizona.edu/AMS/xtal_data/DIFfiles/15285.txt</a> based on this information: <a href="http://rruff.geo.arizona.edu/AMS/CIF_text_files/15285_cif.txt">http://rruff.geo.arizona.edu/AMS/CIF_text_files/15285_cif.txt</a></div><div><br></div><div>I am using CCTBX in Python:</div><div><br></div><div>
<p style="margin:0px">from cctbx.array_family import flex </p>
<p style="margin:0px">from cctbx import sgtbx, crystal, miller, xray</p>
<p style="margin:0px">sgnum = 227</p>
<p style="margin:0px">sg = sgtbx.space_group_info(sgnum).group()</p>
<p style="margin:0px">latticepar = [5.43070, 5.43070, 5.43070, 90, 90, 90]</p>
<p style="margin:0px">dmin = 1.0</p>
<p style="margin:0px">atompos = [['Si',(0.0, 0.0, 0.0)]]</p>
<p style="margin:0px">scatterers = flex.xray_scatterer()</p>
<p style="margin:0px">scatterers.append(xray.scatterer(label=atompos[0][0], site=atompos[0][1]))</p>
<p style="margin:0px">pg = sg.build_derived_point_group()</p>
<p style="margin:0px">sym = crystal.symmetry(space_group=sg,unit_cell=latticepar)</p>
<p style="margin:0px">sps = crystal.special_position_settings(crystal_symmetry=sym)</p>
<p style="margin:0px">structure = xray.structure(special_position_settings=sps,scatterers=scatterers)</p>
<p style="margin:0px">F = structure.structure_factors(d_min=dmin,algorithm='direct').f_calc()</p>
<p style="margin:0px">list(F.amplitudes())</p><p style="margin:0px"><br></p><p style="margin:0px">This gives:</p><p style="margin:0px">[((0, 2, 2), 0.0),</p><p style="margin:0px"> ((0, 4, 0), 120.21765812638594),</p><p style="margin:0px"> ((1, 1, 1), 84.18849550806966),</p><p style="margin:0px"> ((1, 3, 1), 65.48371727205928),</p><p style="margin:0px"> ((1, 3, 3), 57.45438308324155),</p><p style="margin:0px"> ((1, 5, 1), 51.48759686950681),</p><p style="margin:0px"> ((2, 2, 2), 128.54540698861973),</p><p style="margin:0px"> ((2, 4, 2), 0.0),</p><p style="margin:0px"> ((3, 3, 3), 51.48759686950681)]</p></div><div><br></div><div>How come CCTBX give an amplitude of 0.0 for (0,2,2) and (2,4,2)? The measured intensities in the DIFfile above does not show this. Am I missing something?</div><div><br></div><div>Cheers,</div><div>/Allan</div></div>