Computation of phonon for attached input script using quantum espresso displays multiple messages in the output file which state: Eigenvectors exchange needed 13 19. What could be the source of this message?
Pooja Vyas
Take a look: https://lists.quantum-espresso.org/pipermail/users/2017-July/038740.html
Qamar Ul Islam Thanks, but the query in the link is unanswered. However, it appears from the query that it may be due to imaginary frequencies arising for the structure. However, earlier I have worked with unstable structures which had imaginary frequencies, but no such message appeared there.
Hi Pooja Vyas, I'm facing the exact same problem now. Did you find a solution eventually? Thanks.
Abdullah Al Maruf , the message displayed in the output is merely a warning, probably pointing towards instability in structure, which may cause negative frequencies to appear at the end. However, since its just a warning, it wouldn't stop your calculation from running.
Pooja Vyas, thanks for the feedback. Here's the update from my side (in case it's helpful) –
I am using fairly large systems, hence I needed to use few hundred cores at a time with MPI parallelization at HPC. Thus such errors of "Eigenvectors exchange needed..." pretty much forced my calculation to stop proceeding any further. So I used relatively hard pseudopotentials (NCPP stringent) instead, and the issue is fixed now.
Abdullah Al Maruf , Ok. In my case, the run had not got terminated due to the warning, so I hadn't actually tried making any changes in input or number of cores. Good to know that your issue is solved.
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