Negative Thermal parameters

[Yokochi, Alexandre]

Hi,   Basically, your high angle data has unexpectedly high intensities.  I always tell my students that to begin with, ensure you are not collecting data with variable slits, or if you are, that you convert the intensities to fixed slits equivalent properly.   Alex Y   Dr. Alexandre (Alex) Yokochi Assistant Professor Department of Chemical Engineering Oregon State University Corvallis, OR 97331-2702 Phone:  (541)-737-9357 Fax:  (541)-737-4600   -----Original Message----- From: Gerard, Garcia S [mailto:[EMAIL PROTECTED] Sent: Monday, January 31, 2005 9:03 AM To: rietveld_l@ill.fr Subject: Negative Thermal parameters   I'm getting started with GSAS and in all my refinements i get stuck with negative thermal parameters no matter what i do. Is there any tip to get rid of this problem or maybe do i need to learn a little bit more?   Thanks