Stephen, Whether the space group is centrosymmetric or not isn't the issue. The question is whether it is polar or not. P2/n is not polar (i.e. origin defined relative to some symmetry element) but P2 is polar (i.e y coordinate not chosen relative to a symmetry element). Bob Von Dreele
________________________________ From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Sent: Wed 3/31/2004 9:23 PM To: [EMAIL PROTECTED] Dear Robert B.Von Dreele Thank you for your explanation. Therefore GSAS could do the origin fixing for us when the space group is not centrosymmetric. Can I boardly say that? regards, stephen
