[Pw_forum] Symmetry Related Error

[Giovanni Cantele]

I never found such kind of error. However, if I well understand, it seems that you are telling
QE to use a trigonal lattice but then you force it to use a lattice with a different symmetry.

ibrav=-5 corresponds to a trigonal lattice, for which a=b=c and the same angle alpha between
ANY pair of lattice vectors (alpha=beta=gamma).

Probably, the setting you give a=b/=c and beta=gamma/=alpha OVERRIDES any default and you
end up with conflicting settings: ibrav=-5 tells QE to use a trigonal lattice and on this basis some symmetries
are expected, but based on the input lattice parameters (A, B, C, cosAB, cosAC, cosBC) a lattice with different
symmetries is set up.

So, try to answer to this question: do you want a trigonal or an hexagonal lattice? In the first case you should change
the parameters in input, setting up only A and cosBC, in the second you should use ibrav=4 instead. 

My guess is that the second answer is the right not, because trying to open your input with Xcrysden nothing is displayed,
but if I change ibrav=-5 to ibrav=4 a reasonable crystal shows up!

Giovanni


> On 12 Mar 2015, at 03:04, John Shin <joyshin at ucsc.edu> wrote:
> 
> Hello,
> 
> I am an undergraduate learning how to use Quantum Espresso. I get the following error when running my input (which I've attached):
> 
> %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
> task #         0
> from set_sym_bl : error #         1
> some problem with symmetries
> %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
> 
> Any help would be greatly appreciated.
> 
> Best,
> John Shin
> 
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-- 

Giovanni Cantele, PhD
CNR-SPIN
c/o Dipartimento di Fisica
Universita' di Napoli "Federico II"
Complesso Universitario M. S. Angelo - Ed. 6
Via Cintia, I-80126, Napoli, Italy
e-mail: giovanni.cantele at spin.cnr.it
Phone: +39 081 676910
Skype contact: giocan74

ResearcherID: http://www.researcherid.com/rid/A-1951-2009
Web page: http://people.na.infn.it/~cantele