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Hello, all,

I tried to do a phonon calculation on a Ta2O5 system with 4 Ta and 10 O in a unit cell, which is hexagonal. In the INCAR file, I used IBRION=8, and LESPILON=.T. , which indicate a RPA_based calculation. I also used ISYM=2. After it was done, however, I found no eigenvalues and eigenvectors of the dynamic matrix at the end of the OUTCAR file. This is very strange for me, because I did a test for a much simpler case, with 2 atoms in a unit cell, and the OUTCAR there gave the eigenvalues. There is a DYNMAT file, but I also cannot find eigenvalues inside. Could anybody help? Thanks.

what pseudopotential did you use? Maybe using a different potential or treating the electrons differently might help?
Could you post the section from your OUTCAR file that contains the eigenvalues from the simpler case and then the OUTCAR from the Ta2O5 case? Did the simulation complete? Do you have the log or error files? It might be that the system is so large that your convergence criteria were not met? I have found these problems when dealing with large, extended, molecular-type systems.

please check if the job finished regularly.

I found something wrong with the job, but I do not know what happened. At the end of the calculation, PIEZOELECTRIC TENSOR is nearly 0 at every position. What could be the reason of that?