Very probably you should refine preferred orientation 0,0,1. If it take
place you'll see improved adp's.
Dr. Peter Y. Zavalij University Crystallographer
Materials Research Center, SUNY at Binghamton
Tel: (607)777-4298 Fax: (607)777-4623
E-mail:[EMAIL PROTECTED]
http://materials.binghamton.edu/zavalij
-----Original Message-----
From: Yokochi, Alexandre [mailto:[EMAIL PROTECTED]]
Sent: Friday, July 13, 2001 1:24 PM
To: '[EMAIL PROTECTED]'
Subject: Negative displacement params in neutron refinement
Hi all,
I have neutron data (constant wavelength) I have been working on and
the displacement parameters of most atoms turn out to be negative along one
axis (c in hexagonal setting). The material has relatively low absorption
coefficient (mu*r approx .5), and (as expected) when a cylindrical
absorption correction is applied, the displacement parameters are still
negative. I would like to hear any suggestions of possible causes. Though
the structure is well known and refined multiple times (including by me from
single crystal for related systems) I favour wrong symmetry / space group as
the cause.
Thanks, AlexY
Dr. Alexandre F. T. Yokochi
Assistant Professor (Senior Research)
Director, X-ray Crystallographic Facilities
Department of Chemistry
Oregon State University
Corvallis, OR 97331-4003
Ph# (541) 737-6724 Email: [EMAIL PROTECTED]
Fax# (541) 737-2062 Web Page: crystal.chem.orst.edu/~alexy (temporarily
unavailable)
