[Pw_forum] symmetry selection in CELL_PARAMETERS

[Paolo Giannozzi]

On Dec 4, 2006, at 7:57 , W. YU wrote:

> 1. I tried to do a antiferromegnetic calculation. I know it is an  
> insulator
> with a small gap, but for such a calcultion, I have to add smearing  
> to change the occupancy of the electrons in order for the code to  
> work.
> Am I doing it right or there is an alternative ?

there are many alternatives, but smearing works for both metals
and insulators, if properly chosen (i.e. small for insulators)

> 2. I tested calculating the  elastic constants using stain-energy  
> method
> with pwscf. I set the ibrav=0 and provided the additional card  
> CELL_PARAMETERS. But there is a symmetry selection for this card.  
> Either CUBIC or HEXGONAL. I know the symmetry before applying the  
> strain (say cubic).

then there is no problem: after applying a strain, the symmetry
group will be a subgroup of the unstrained symmetry group

Paolo
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Paolo Giannozzi, Democritos and University of Udine, Italy