>I'm trying to do a refinement on Valentinite. However, when I use the unit
>cell data from the ICSD demo server (http://barns.ill.fr/dif/icsd/index.html)
>I get very different relative intensities than what I observe in my powder
>pattern, and that of the ICDD pattern (11-689 generated by the NBS).
There are more recent determinations of the structure of orthorhombic Sb2O3
in the full ICSD.
Svensson,C. (1974) Acta Crystallogr.,Sect. 30 458-461
The crystal structure of orthorhombic antimony trioxide, Sb2 O3
cf:
Buerger,MJ. (1936) Am.Miner 21 206-207
The crystal structure of valentinite
In particular you might try orthorhombic Sb2O3 as determined by
Svensson(1974),
which has the same Pccn space group as that of Buerger(1936) but with
different
coordinates. (Svensson,C. (1975) Acta Cryst. 31 2016-2018 also reports on the
cubic phase).
N *-Sb2O3-Svensson C 30 (1974) P. 458-461
C 4.911 12.464 5.412 90. 90. 90.
S GRUP P C C N
A Sb1 0.04149 0.12745 0.17845 0.00000 1.00000
A O1 0.25000 0.25000 0.02290 0.00000 1.00000
A O2 0.15200 0.05910 0.85540 0.00000 1.00000
N *Valentinite-Sb2O3-Buerger M J 21 (1936) P. 206-2
C 4.92 12.46 5.42 90. 90. 90.
S GRUP P C C N
A Sb1 0.12150 0.20700 0.17500 0.00000 1.00000
A O1 0.25000 0.25000 0.92500 0.00000 1.00000
A O2 0.89000 0.15600 0.17500 0.00000 1.00000
There was also a (relatively minor) error in the ICSD-for-WWW pattern
calculation where the occupations and temperature factors were mixed up
(corrected yesterday thanks to Colin Greaves) so you should also repeat
that calculation.
>The Lazy PulverIx data file gives this warning when calculating the pattern:
> Crystal system specified on CELL card and on GROUP card are not consistent
It always gives that message, and you can ignore it :-)
Alan Hewat, ILL Grenoble, FRANCE <[EMAIL PROTECTED]> tel (33) 4.76.20.72.13
ftp://ftp.ill.fr/pub/dif fax (33) 4.76.20.76.48 http://www.ill.fr/dif/
