Momentum Matrix elements

[manuel_engel1]

Unfortunately, I cannot reproduce your issue. When I run the calculation you have uploaded together with the new INCAR that you have posted, it gives me non-zero entries in the WAVEDERF file. What VASP version are you using to run these calculations?

As a side note, when you use ALGO=exact, there is no need to do run so many electronic minimization steps, so you don't have to specify NELMIN. It could only potentially be relevant for ALGO=normal or similar.

[kaynat_kalvi]

Hi, please update me. Thanks

[manuel_engel1]

Since I cannot reproduce your issue, I'm unfortunately unable to give you any further advice. If you tell me the VASP version that you are using, it might give new insights. You may also upload all the input files of the problematic VASP calculation as a zip archive so that I can verify the problem again. This will make absolutely sure that what I have on my side is identical to what you have on your side. However, with what you have posted so far, I cannot reproduce the issue that you see with all zeroes in the output.

[kaynat_kalvi]

Hi,
Thanks for your responses, i now have a WAVEDERF file, now I am calculating oscillator strength from VasP using (https://www.vasp.at/wiki/index.php/Plot ... ture_of_Si) and using the formula = 2 |P|^2 /(m_e (Ec-Ev)), here P^2 are the sum of squares of last 6 columns of WAVEDERF file, and comparing both the results.
For this comparison, I am confused,
1. the oscillator strength values I got in vasprun.xml file after BSE calculation, corresponds of particular eigenvalue, How do I know that which eigenvalue corresponds to which n,k?
for-example for Si I need the transition from to CB which is n=9 from the VBs which are n=5 6 7 8 (having SOC),at k=0 (Gamma), and I want to locate this in the oscillator strength values I am getting out of vasp. please help me understand this

[manuel_engel1]

I'm glad that you were able to obtain a WAVEDERF file.

1. the oscillator strength values I got in vasprun.xml file after BSE calculation, corresponds of particular eigenvalue, How do I know that which eigenvalue corresponds to which n,k?

The BSE eigenvalues do not correspond directly to Kohn-Sham eigenstates but rather to BSE eigenstates. Therefore, a direct comparison is not generally possible (unless you are in the independent-particle approximation).
The oscillator strengths of the BSE states are ordered together with the corresponding BSE eigenvalues in the XML file. However, there is no k-dependence as these are the oscillator strengths corresponding to some BSE excitations. If you are interested in k-dependence, you can look at the BSEFATBAND file that contains information about the transition energies underlying a particular BSE eigenstate. This is nicely explained in the tutorial that you have linked.