Dear Doinita (and others), I'm assuming this is a GSAS question. The tic marks show the ideal position of the reflections according to Bragg's Law. The real peaks can be "out of position" for a variety of reasons including a non zero ZERO. Most usually for ordinary x-ray powder data the sample displacement is the usual systematic error. Refine "shft" - found in the profile function. A badly zeroed diffractometer will also show offsets. If the offset is small in the plots & the fit is OK then don't worry about the plot. If big then I'd look at the raw data to make sure the "START" value on the "BANK" record is correct. Bob Von Dreele
________________________________ From: Doinita E Neiner [mailto:[EMAIL PROTECTED] Sent: Fri 6/25/2004 4:57 PM To: [EMAIL PROTECTED] Hello, Does anybody know how do you move the thick marks in the peaks position because though I have a good fit they are all shifted to the left. Shall I refine ZERO? Anticipated thanks to any kind of suggestions. Doinita
