On Friday 17 November 2006 16:42, Irina POZDNYAKOVA wrote:
> I just tried to compare four different software: FindIt, Diamond,
> PowderCell and FullProf to calculate structure for alpha-alumina using ICSD
> #51687 file (Materials Science Forum(2001), 378, 288-293,Unit Cell
> 4.7597(1) 4.7597(1) 12.9935(3)). I used the same geometry (Bragg-Brentano),
> wavelength, profile parameters, no background, same space group settings.
> But all four patterns have different intensity, and structure factors also
> (for software that gives a possibility to get one). I can not understand
> why the structural factors differ. The visualized structures are exactly
> the same. Maybe somebody knows? Thank you in advance,
Two possibilities to explain different structure factors:
- R-3c can either use the rhomboedral or the hexagonal unit cell - maybe the
default choice for the spg changes between programs (that would produce very
different patterns !)
- If the structure factor differences are small, maybe it is that they are
using different anomalous scattering factors (though for al2o3 these should
be small) ?
Vincent
--
Vincent Favre-Nicolin
Université Joseph Fourier
http://v.favrenicolin.free.fr
ObjCryst & Fox : http://objcryst.sourceforge.net
