Our system has double mirrors and I could never get FCJ to give as good a fit, but then that may be a peculiarity of these optics. My memory is a bit hazy so I can't remember what function the simple axial model uses, but I don't think it's a function of diffractometer characteristics. Topas is flexible enough that you can convolute just about any equation you care to come up with with any kind of angular dependence (or not), but they do make your size/strain results somewhat useless if they are added as an afterthought (e.g. to fit turbostratic disorder).
Pam Dr Pamela Whitfield CChem MRSC Energy Materials Group Institute for Chemical Process and Environmental Technology Building M12 National Research Council Canada 1200 Montreal Road Ottawa ON K1A 0R6 CANADA Tel: (613) 998 8462 Fax: (613) 991 2384 Email: <mailto:[EMAIL PROTECTED]> ICPET WWW: http://icpet-itpce.nrc-cnrc.gc.ca -----Original Message----- From: Maxim V. Lobanov [mailto:[EMAIL PROTECTED] Sent: June 4, 2004 10:27 AM To: [EMAIL PROTECTED] In Topas there are two options for treating low-angle asymmetry using diffractometer characteristics (i.e., "fundamental parameters") called "simple axial model" and "full axial model". But (this is my impression only) it seems that FCJ (Finger et al) approach works equally well. Starting from Topas2.1 it is implemented too, and you can easily compare. On the other hand, a very useful feature of Topas is the possibility to treat irregular peak asymmetry originating from "sample effects"... Sincerely, Maxim. >Again, does this approach take care of low angle peak >asymmetry better? __________________________________ Maxim V. Lobanov Department of Chemistry Rutgers University 610 Taylor Rd Piscataway, NJ 08854 Phone: (732) 445-3811
