[QE-users] Keep the symmetry during a calculation

[Paolo Giannozzi]

On Sat, Sep 15, 2018 at 10:09 AM, Carina Backtorp <
carinabacktorp at hotmail.com> wrote:

>
> 1) When doing an vc-relax calculation in espresso, I expected that once
> the symmetry was given (ibrav=1) espresso should keep the symmetry during
> all the calculation
>

it does. Note however that the symmetry of the lattice is just part of the
story.  QE finds the starting symmetry of the crystal, and this is what is
kept during the run (although occasionally, numerical noise and poor
convergence may lead to the loss of the original symmetry). If the starting
symmetry is not cubic, the final cell may lose its original cubic aspect.
Also note that QE uses its own criteria for symmetry, that may differ from
criteria used by other codes, so something that QE deems cubic may be
classified as orthorhombic by a pickier code

Paolo


>
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-- 
Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,
Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
Phone +39-0432-558216, fax +39-0432-558222
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