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[EMAIL PROTECTED] wrote on 05/02/2006 05:14:00 PM: > *** For details on how to be removed from this list visit the *** > *** CCP4 home page http://www.ccp4.ac.uk *** > > > Hi, > I Have a question about permuting crystal indices. When I compare two > crystal data sets to get crossR value to know how isomorphous they > are, I need to permute the indices of one of the crystal. Both of my > crystals have space group P212121. I was told to permute HKL to LKH, > HLK, and KHL. I do not have a clear mind the principle. For example, > by whole arrangement, there will be 6 possibilities for the > permutation. Why only four exist here? The second question is more > important: if I want to change from HKL to KHL, the new indices are > (0 -1 0 -1 0 0 0 0 -1), not (0 1 0 1 0 0 0 0 1). Why there > is minus sign in the indices? > > Could anyone recommend me one paper or book to read to solve my puzzle? > > Your help is greatly appreciated! Hi Qun - To permute the axes of your orthorhombic system, you need to preserve the handedness of your axes, i.e. you must be able to rotate one set of axes onto the other. This means you only have three choices: HKL, KLH, and LHK. The other three choices (including KHL) invert the coordinate system, thus reversing the sign of any anomalous signal you might have (I+ and I- get swapped). However, I should point out that there should be only one consistent choice of your axes. If your reference dataset has a=40 A, b=65 A, and c=100 A, then all other datasets should be permuted to give the same set of abc. So you don't need to test all three, and if you used the same indexing program for all your data you shouldn't need to reindex at all. As for your second question, the matrix you gave converts H,K,L -> -K,-H,-L. You can then flip this upside down (H,K,L -> K,H,-L) and rotate it 180 degrees about the c axis (H,K,L -> -H,-K,L) to give you the matrix you were looking for, i.e. they're equivalent. However, you shouldn't be using this matrix anyway... Sorry I don't have a paper to point you to. - Matt -- Matthew Franklin phone:(917)606-4116 Senior Scientist, ImClone Systems fax:(212)645-2054 180 Varick Street, 6th floor New York, NY 10014 Confidentiality Note: This e-mail, and any attachment to it, contains privileged and confidential information intended only for the use of the individual(s) or entity named on the e-mail. If the reader of this e-mail is not the intended recipient, or the employee or agent responsible for delivering it to the intended recipient, you are hereby notified that reading it is strictly prohibited. If you have received this e-mail in error, please immediately return it to the sender and delete it from your system. Thank you.
