[Pw_forum] The phonon frequency unit in matdyn.x v5.0

[GAO Zhe]

Dear QE developer and users:
I am using QE 5.0 now.
I am not sure whether I did not read the manual carefully. But when I use the matdyn.x as in QE 4.3.2, the output unit became different.

Detail:
In matdyn.x v4.x, one did not have to set the parameters amass(i) and the element mass can be read from IFCs file. The output frequency was in cm^(-1) unit.
Now, in matdyn.x v5.0, if I did not set amass(i), the output frequency would be in some other unit. I though it was THz, but I compared it with the output from matdyn.x v4.3.2 by the same IFCs, the arbitrary value was a little bit higher than when unit in THz. The same issue was found when calculate phonon DOS.
However, if I added amass(i) parameters, all of the result would be in cm^(-1) unit.
The comparason for with and without amass(i) in matdyn.x v5.0 is shown as the accessory, which was from the example of Fe_AFM in PlotPhon.

By the way, when I used 'crystal' method for ASR in matdyn.x v4.3, the results from with and without amass(i) has some different in low frequency acoustics bratches as:
With amass(i):
            0.010000  0.000000  0.000000
    6.5359    3.0829    3.2829  155.3803  173.4756  173.4207
  232.7133  232.7937  237.6018  280.0328  280.1047  283.2520
....
            0.020000  0.000000  0.000000
   13.0533    6.1661    6.5649  155.4117  173.5031  173.2838
  232.4662  232.7895  237.6108  279.8124  280.0984  283.2260
....
Without amass(i):
            0.010000  0.000000  0.000000
    3.0829    3.2829    6.5359  155.3803  173.4207  173.4756
  232.7133  232.7937  237.6018  280.0328  280.1047  283.2520
....
            0.020000  0.000000  0.000000
    6.1661    6.5649   13.0533  155.4117  173.2838  173.5031
  232.4662  232.7895  237.6108  279.8124  280.0984  283.2260
....


--
GAO Zhe
CMC Lab, Materials Science & Engineering Department,
Seoul National University, South Korea
 
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