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[Xavier Gonze <xavier.gonze@uclouvain.be>]

An answer has been posted on http://forum.abinit.org .
Best regards,
Xavier

On 26 Jan 2010, at 09:53, Davide Sangalli wrote:

> Dear forum,
> I've a question on symmetries.
> I'm running abinit on some cnt and in particular the (5,5) and the  
> (8,8)
>
> ********************************************************
> For the (5,5) in the log files abinit says:
>  symanal : COMMENT -
>   The Bravais lattice determined only from the primitive
>   vectors, bravais(1)=  6, is more symmetric
>   than the real one, iholohedry=  2, obtained by taking into
>   account the atomic positions.
>  symspgr : the symmetry operation no.   1 is the identity
>  symspgr : the symmetry operation no.   2 is an inversion
>  symaxes : the symmetry operation no.   3 is a 2_1-axis
>  symplanes : the symmetry operation no.   4 is a mirror plane
>  symspgr : spgroup=  11  P2_1/m   (=C2h^2)
>
> but then reports 2 symmetries in the report file:
>  symmorphi         0
>     symrel    1  0  0   0  1  0   0  0  1       1  0  0   0  1  0    
> 0  0 -1
>     toldfe    1.00000000E-06 Hartree
> ***************************************************************
>
> On the other hand for the (8,8) in the log abinit says:
>  symanal : COMMENT -
>   The Bravais lattice determined only from the primitive
>   vectors, bravais(1)=  6, is more symmetric
>   than the real one, iholohedry=  2, obtained by taking into
>   account the atomic positions.
>  symspgr : the symmetry operation no.   1 is the identity
>  symspgr : the symmetry operation no.   2 is an inversion
>  symaxes : the symmetry operation no.   3 is a 2-axis
>  symplanes : the symmetry operation no.   4 is a mirror plane
>  symspgr : spgroup=  10  P2/m   (=C2h^1)
>
> and then reports 4 symmetries in the report file:
>  symmorphi         0
>     symrel    1  0  0   0  1  0   0  0  1      -1  0  0   0 -1  0    
> 0  0 -1
>              -1  0  0   0 -1  0   0  0  1       1  0  0   0  1  0    
> 0  0 -1
>     toldfe    1.00000000E-06 Hartree
> ******************************************************************
>
> I do not understand what is going on.
> Shouldn't there be 4 symmetries in both ?
>
> Regards,
> Davide