[Pw_forum] Eigenvectors Exchange Needed in Phonon output

[GAUTAM SHARMA]

Dear QE users,

I am doing phonon calculations on Monolayer of BiI3 and I am getting a
message in the output file as following:
 Dynamical matrices for ( 3, 3, 1)  uniform grid of q-points
     (   3q-points):
       N         xq(1)         xq(2)         xq(3)
       1   0.000000000   0.000000000   0.000000000
       2   0.333333333   0.192450090   0.000000000
       3   0.666666667   0.000000000   0.000000000
Eigenvectors exchange needed    5    9
Eigenvectors exchange needed    7   11
Eigenvectors exchange needed    9   10
Eigenvectors exchange needed   11   12
Eigenvectors exchange needed   17   21
Eigenvectors exchange needed   19   23
Eigenvectors exchange needed   21   22
Eigenvectors exchange needed   23   24

What is meaning of this message?
Particularly, I am getting some negative frequencies in the
phonon-dispersion. So, My question is the following :
Can the above message has any connection to why I am getting negative
frequencies? Please suggest.

Regards,
Gautam Sharma
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.quantum-espresso.org/pipermail/users/attachments/20170724/67db1936/attachment.html>