Hello, we have a relatively new Bruker diffractometer with Cu source and diffracted-beam graphite monochromator. When collecting the patterns, I found it difficult to refine them to low chi**2, even for the standard supplied by the manufacturer. What I also found is that if I refine the POLA variable in GSAS, the chi**2 improves a lot (from 18 to 3.5 for quartz standard). However, the POLA (polarization fraction) refines to 2.5 which is too much.
Can anyone suggest if this is a diffractometer problem or the POLA variable correlates with other variables that need to be taken care of in GSAS? What should be the value of POLA for a standard diffractometer with the graphite monochromator? Thank you, Juro Majzlan ---------------------------------- Juraj Majzlan Institute of Mineralogy and Petrology Albert-Ludwig-University of Freiburg Albertstrasse 23b Freiburg, D-79104, Germany telephone +49-761-203-6416 fax +49-761-203-6407 http://www.minpet.uni-freiburg.de/sites/personen/majzlan.html
