Request to clarify AMSET inputs about amset

[lycheelee54]

Dear rajanpir and Alex,

I am also tangling with the "pop_frequency" tag in the setting.yaml these days. In AMSET example, it happens that both GaAs and Si system only have one LO-TO splitting phonon band, so it seems that LO happens to be the phonon band with the highest phonon frequency. But in SnS system I calculate, there seems to be more than one optic phonon band that are splitting. So should I still use "the frequency of the highest phonon band" as the input in "pop_frequency" tag?

Also I have read the part about using command
amset phonon-frequency
to extract the weighted-sum polar optic phonon frequency. Is this method helps in solving the problems I met in SnS? Anyway ,I ran the command but only get a effective frequency equals 0 THz. I don't know if this means my DFPT calculation goes wrong?

FYI, I have attached the phonon dispersion of SnS I calculated here and the output after I entered the command amset phonon-frequency in SnS DFPT calculation directory:

Frequency Weight

---

  -0.01      0.00
  -0.01      0.00
  -0.00      0.00
  -0.00      0.00
  -0.00      0.00
  -0.00      0.00
   0.00      0.06
   0.00      0.94
   0.00      0.00
   0.00      0.00
   1.11      0.00
   1.92      0.00
   2.00      0.00
   2.34      0.00
   2.76      0.00
   2.86      0.00
   5.12      0.00
   5.43      0.00
   5.56      0.00
   6.20      0.00
   6.47      0.00
   6.61      0.00
   6.63      0.00
   8.25      0.00

effective frequency: 0.00 THz

Best,
Zhi

[utf]

Hi @rajanpir and @lycheelee54,

Thanks for your questions and your interest in AMSET. I am hoping to keep the GitHub only for bug reports from now on. If you have questions on how to use the code, please instead post them to the help forum: https://matsci.org/c/amset

I have moved both of your questions to the forum and answered them there:
@rajanpir: https://matsci.org/t/request-to-clarify-amset-inputs/4731
@lycheelee54: https://matsci.org/t/question-on-polar-optical-phonon-frequency/4733

Please continue the discussion on the forum.

Best,
Alex

[lycheelee54]

Hi Alex,

It seems that MATSCI doesn't support any file uploading except pictures. I am sorry that I have to upload my input file for DFPT run here. We can still discuss at MATSCI forum.
INCAR.txt
OUTCAR.txt
POSCAR.txt
KPOINTS.txt
OSZICAR.txt

Thanks,
Zhi

[utf]

Hi Zhi, can you also send over the input/output files of your relaxation?

[utf]

Also, I notice you are using a Monkhurst Pack grid rather than Gamma centred.

For AMSET itself, you need to use a Gamma centred grid (it doesn't work well with Monkhurst Pack). I would also recommend trying your relaxation and DFPT calculations with Gamma centred too.

[lycheelee54]

Hi Alex,

Here are my input/output files of relaxation (the OUTCAR is over 10 MB and cannot be upload, so I have to substitute it with a log file). It never occurs to me that the problem should lie in k-mesh. Thanks for the suggestion. I'll try rerun the relaxation and DFPT with Gamma centerd k mesh.

Thank you,
Zhi
KPOINTS.txt
POSCAR.txt
CONTCAR.txt
output.txt
INCAR.txt

[utf]

Hi @lycheelee54. The CONTCAR from your relaxation does not match the POSCAR you used in the DFPT calculation. Can you check you are using the full converged structure for your DFPT run.

[lycheelee54]

Hello Alex,

Sorry I uplaoded the wrong POSCAR for DFPT calculation. Anyway, I have rerun both the relaxation and DFPT calcualtion, with tight convergence criterion and Gamma centered KPOINTS. But I still get the abnormal 0 THz effective frequency. I find out that POSCAR hasn't changed much and all the other outputs are to some extent similar with the old ones. It seems that problem doesn't lie in POSCAR or KPOINTS? I still attached all the input/output files for your information. Thanks you so much for the patient response and kindly help.
INCAR_relax.txt
KPOINTS_relax.txt
POSCAR_relax.txt
CONTCAR_relax.txt
OUTCAR_relax.txt
INCAR_DFPT.txt
KPOINTS_DFPT.txt
POSCAR_DFPT.txt
OSZICAR_DFPT.txt
OUTCAR_DFPT.txt

Thanks,
Zhi

[utf]

Hi @lycheelee54, I cannot see anything wrong in your input files, however your DFPT calculation output is bad (contains 10 zero frequency gamma point phonon modes).

The only thing I can think of is that your VASP version is very old (v5.3.1) I know there have been many bug fixes since then, so perhaps they fixed something to do with DFPT. I would suggest seeing if a more recent VASP version fixes your problem.

Best,
Alex

[lycheelee54]

Hi Alex,

It works! After I changed to VASP 5.4.4 and reran the DFPT calculation, The output of effective frequency is now like this:
Frequency Weight
-0.01 0.00
-0.01 0.00
-0.00 0.00
1.11 0.00
1.44 0.00
1.62 0.00
1.92 0.03
1.99 0.00
2.01 0.00
2.34 0.00
2.76 0.00
2.88 0.11
4.10 0.33
4.74 0.00
5.13 0.21
5.42 0.23
5.57 0.00
5.62 0.00
6.06 0.00
6.21 0.04
6.49 0.00
6.62 0.00
6.64 0.05
8.25 0.00
effective frequency: 4.62 THz

It now correctly shows 3 zero frequency phonon modes corresponding to 3 acoustic phonon modes. Thank you so much!

Best,
Zhi