The selection rule for R-3m is h-k =3n +- 1. Are you per chance working with delithiated or charged lithium battery materials? You can get some rather wierd broadening effects that we looked at a couple of years ago (which is why I know the selection rule!) Pam
________________________________ From: Radovan Cerny [mailto:[EMAIL PROTECTED] Sent: Wed 14/02/2007 11:21 AM To: [email protected] Subject: Re: Strange peak positions If the asymmetry of the profiles is also anisotropic I guess on stacking faults on close packed planes 00l. However, the HKL law looks little bit strange to me ... Radovan Jae-Ho Chung a écrit : > Dear all, > > I would appreciate any comments for the following problem. > > I have been studying samples (ABO2) with a rather simple R -3 m structure. > Although I had expected their neutron powder diffraction refinement should be > simple, I encountered a strange problem. Many of the peak positions are quite > off from where they should be. For instance, I singled out and refine (0 0 3), > (0 0 6), (0 0 9) & (0 0 12) separately. Quite strangely, (0 0 6) peak is > noticeably off when (0 0 3), (0 0 9) and (0 0 12) are good. For full > refinements, such problem shows up for several peaks. I see same trend from > data measured at two different instruments: CW and TOF. FYI, the peak profiles > are quite Lorentzian and asymmetric. > > Anybody have experiences such a problem, and/or have suggestions what is going > on? I would greatly appreciate. > > Jae-Ho > > ************************************* > Jae-Ho Chung, Ph.D. > NIST Center for Neutron Research > 100 Bureau Drive, Stop 8562 > Gaithersburg, MD 20899-8562 > Tel. 301-975-8369 (office) > 301-975-5085 (SPINS) > 240-506-8389 (cell) > Fax. 301-921-9847 > e-mail: [EMAIL PROTECTED] (work) > [EMAIL PROTECTED](personal) > ************************************* -- Radovan Cerny Laboratoire de Cristallographie 24, quai Ernest-Ansermet CH-1211 Geneva 4, Switzerland Phone : [+[41] 22] 37 964 50, FAX : [+[41] 22] 37 961 08 mailto : [EMAIL PROTECTED] URL : http://www.unige.ch/sciences/crystal/cerny/rcerny.htm
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