<html><body><div style="color:#000; background-color:#fff; font-family:Courier New, courier, monaco, monospace, sans-serif;font-size:10pt"><div><span>Hi David,</span></div><div><span><br></span></div><div><span>cctbx does not include lists of reflection conditions as you find them in the International Tables.<br></span></div><div><span><br></span></div><div><span>It is very easy and fast to derive the reflection condition for a given hkl directly from the symmetry operations. See the code near the top of cctbx/sgtbx/miller.cpp. This is what we use for all practical applications. For example:</span></div><div><br><span></span></div><div><span> from cctbx import sgtbx</span></div><div><span> sg = sgtbx.space_group_info("19").group()</span></div><div><span> print sg.is_sys_absent((1,2,3))<br></span></div><div><span> print sg.is_sys_absent((0,0,3))<br>
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<div><span>I have C code given to me by Maxim Larine and Slava Klimkovich in 1997 which computes the conditions, but it involves inefficient grid searches.</span></div><div><br><span></span></div><div><span>I think a good solution would be to tabulate the conditions for the 230 reference settings and figure out the transformation law to obtain the conditions for arbitrary settings via a change of basis. But I yet have</span></div><div><span>to find a practical motivation for spending the effort implementing this.</span></div><div><br></div><div>If you find that Phil has a solution, it would be nice to move it into</div><div>cctbx.</div><div><br></div><div>Ralf</div><div><br><blockquote style="border-left: 2px solid rgb(16, 16, 255); margin-left: 5px; padding-left: 5px;"><div style="font-family: Courier New, courier, monaco, monospace, sans-serif; font-size: 10pt;"><div style="font-family: times new roman, new york, times, serif; font-size: 12pt;"><font
face="Arial" size="2"><hr size="1"><b><span style="font-weight:bold;">From:</span></b> David Waterman <dgwaterman@gmail.com><br><b><span style="font-weight: bold;">To:</span></b> cctbxbb@phenix-online.org<br><b><span style="font-weight: bold;">Sent:</span></b> Saturday, June 4, 2011 3:28 AM<br><b><span style="font-weight: bold;">Subject:</span></b> [cctbxbb] reflection conditions for non-standard settings<br></font><br>
<div id="yiv687426080">Hi,<div><br></div><div>I'm new to cctbx and to this mailing list, so please let me first apologise if the answer to this question should be obvious, or lies in the archive.</div><div><br></div><div>I want a list of general reflection conditions for all space groups and settings listed in the CCP4 file syminfo.lib. At first I thought I could get this information from the online version of ITC vol A, but I soon realised that only certain standard settings are included. To avoid deriving them all by hand from the symop and cenop lines, I wonder if there is a foolproof way I can get this information from cctbx, but I don't know where to begin. Perhaps something in sgtbx?</div>
<div><br></div><div>Many thanks<br clear="all"><br>-- David<br>
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