[Wien] Ti2O3 structure factors...

[Peter Blaha]

> I am calculating structure factors with WIEN and as a test I have punched out
> the HKL-file for the Ti2O3 example included in WIEN2K. When I do this using
> lapw3 I get many negative values for F. Is there a phase information included
> in the sign or are these really negative factors ?

The structure factor can really be negative due to the pahasefactors.
Of course experimentally you measure only the modulus and solving this
"phase-problem" is one of the major issues for exp. X-ray diffraction.


> And my second question is: In the manual it is stated that the cell parameters
> in the case of a rhombohedral spacegroup shall be given in the hexagonal
> setting, but the atomic coordinates shall be given in rhombohedral system.
> But in the example struct-file the cell parameters are given as:
>
> 9.7472066 9.747206625.721060090.000000090.000000090.0000000

Of course, gamma should be 120. However, if lattic is H or R, gamma will
be set internally to 120, so it should not matter in the struct file.

> So how does WIEN handle these cases ? And as a consequence: Which setting are
> the HKLs refering to I obtain in the Ti2O3.output3 ?

Internally WIEN uses the smaller rhombohedral cell and thus also the
HKLs refer to the R cell.

                                      P.Blaha
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Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
Phone: +43-1-58801-15671             FAX: +43-1-58801-15698
Email: blaha at theochem.tuwien.ac.at    WWW: http://info.tuwien.ac.at/theochem/
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