A
couple of things that can cause mischief are surface roughness and beam
overspill in lab data. The first you can deal with in software, GSAS
included. The second simply requires care in data collection,
especially with Bragg-Brentano reflection data, where the beam footprint
increases alarmingly at lower angles. Beam-overspill is one of those
things that should be obvious but still jumps up and bites you from
time-to-time!
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:
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ICPET WWW: http://icpet-itpce.nrc-cnrc.gc.ca
-----Original Message-----
From: Gerard, Garcia S [mailto:[EMAIL PROTECTED]
Sent: January 31, 2005 12:03 PM
To: [email protected]
Subject: Negative Thermal parametersI'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
