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[Marino Vetuschi Zuccolini <zucco@dipteris.unige.it>]

Prof. Gonze,
I know that the right coordinates are like this matrix (as in MgCO3)
  0.0         0.0         0.0
  0.5         0.5         0.5
  0.25        0.25        0.25
 -0.25       -0.25       -0.25
  0.5274     -0.0274      0.25
  0.25        0.5274     -0.0274
 -0.0274      0.25        0.5274
 -0.5274      0.0274     -0.25
 -0.25       -0.5274      0.0274
  0.0274     -0.25       -0.5274

but my question were suggested only for comparison between different  
codes without any change of the coordinates.

Many thanks again

m.

On 26 Jun 2009, at 12:18, Xavier Gonze wrote:

> On 26 Jun 2009, at 12:04, Marino Vetuschi Zuccolini wrote:
>
> > Hello to all,
> >
> > playing with a rhombohedral structure (carbonate minerals as  
> > calcite, R-3c, class 167 H-M) with abinit, I found that the  
> > fractional coordinates matrix here in the following it is not  
> > recognized as a member to that class but to class 148 H-M. it is a  
> > problem due to an insufficient number of digits or it is my fault?   
> > Other software recognize unambiguously the structure as R-3c.
>
> You should have at least
>
> C 0.25 0.25 0.25
> C 0.75 0.75 0.75
>
> and the O coordinates should be corrected also ...
>
> X.
>
> > Many thanks for your help
> >
> >
> > Fe1      0.000000000  -0.000000000   0.000000000
> > Fe2      0.500000000   0.500000000   0.500000000
> > C        0.249919131   0.249919131   0.249919131
> > C        0.750080869   0.750080869   0.750080869
> > O       -0.019563280   0.519848977   0.249446873
> > O        0.519848977   0.249446873  -0.019563280
> > O        0.249446873  -0.019563280   0.519848977
> > O        0.019563280   0.480151023   0.750553127
> > O        0.480151023   0.750553127   0.019563280
> > O        0.750553127   0.019563280   0.480151023
> >
> >
> >
> > *******************************************************
> > Marino Vetuschi Zuccolini
> > zucco@dipteris.unige.it
> > Researcher / Geochemist
> > Laboratory of Geochemistry
> >
> > DIPartimento per lo studio della TErra e delle sue RISorse -  
> > Università  di Genova
> > Tel. ++39 010 3538136 Fax. ++39 010 352169
> > Corso Europa 26, 16132 - Genova - Italy



*******************************************************
Marino Vetuschi Zuccolini
zucco@dipteris.unige.it
Researcher / Geochemist
Laboratory of Geochemistry

DIPartimento per lo studio della TErra e delle sue RISorse -  
Università  di Genova
Tel. ++39 010 3538136 Fax. ++39 010 352169
Corso Europa 26, 16132 - Genova - Italy