[Wien] Structure Factors and unit cell content

[Georg Eickerling]

Hi again !

> For example you can use the data which you have already calculated
> with lapw3. If you want to transform them into the structure factors
> for the complete b-centered cell you should simply multiply the
> obtained values by 2 for the case h+l=2n and by 0 when h+l=2n+1.

Is this really that simple in the case of a body-centered cell ? The 
orientation of the primitive cell is different from that of the original 
body-centered cell, so I would think that the HKL Indices do not match each 
other. 
Apart from that I have tried to refine the structure with the calculated HKL 
and if there is only a constant factor which has to be multiplied for all HKL 
this should be covered by the refinement of the scaling factor - which is not 
the case.

Regarding your note on the extinction rules: The cell is body-centered, so I 
would have the reflection-condition h+k+l=2n. This is already taken care of 
by lapw3 as it seems, because there are only such hkl in the output-list. 

regards

Georg



> > Dear WIEN users,
> >
> > I am trying to calculate structure factors for a carbide contaning Sc and
> > Fe. The spacegroup of the compound is Immm (No. 71), i.e. I have a
> > orthorhomic, b-centered cell. There are 1 Fe, 2 Sc and 4 C Atoms in the
> > asymmetric unit, the atoms are located at the special positions 2b(Fe),
> > 2d(Sc1), 4i(sc2) and 8l(C). The complete cell-content is 2Fe, 6Sc and 8C.
> >
> > The calculations converged without problems and the structure looks fine
> > when I plot it using xcrysden.
> >
> > Then I tried to calculate a HKL File using lapw3. In the output I obtain
> > an F000 value of 113 which is the sum of 3xSc, 1xFe and 4xC. This is the
> > content of the reduced primitive, not body-centered cell.
> >
> > Is there a way to make lapw3 use the complete b-centered cell for the
> > calculation of the Intensities so they are directly comparable with
> > experimental data ?
> >
> > Thank you for any help !
> >
> > Georg
> >
> >
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>
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-- 
============================
Dipl.-Chem. Georg Eickerling
Universität Augsburg
Institut für Physik
Lehrstuhl für Chemische Physik und Materialwissenschaften
Universitätsstr. 1
86159 Augsburg

E-Mail:	georg.eickerling at physik.uni-augsburg.de
Phone:	+49-821-598-3358
FAX:	+49-821-598-3227
WWW:	http://www.physik.uni-augsburg.de/cpm/
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