[QE-developers] Matrix Elements of the Momentum Operator

[Rafal Korlacki]

Hello,

I believe there is a bug in the routine write_p_avg in all the versions 6 of QE. Specifically, in the following fragment:

     !
     !   Compute the number of occupated bands at this k point
     !
     DO ibnd = 1, nbnd
        IF (et (ibnd, ik)<=ef) nbnd_occ = ibnd
     ENDDO

It seems that the variable ef=0 rather than whatever the right number is, and the code gets confused about which bands are occupied and which are not. If I replace ef with a number corresponding to an energy somewhere within the bandgap for a particular material, the output is consistent with earlier versions of QE, like 5.3.0. Otherwise the code calculates overlaps between the wrong band pairs, the format of the output varies between k-points, etc. I tested this behavior for QE 6.2 to 6.5.

Best regards,

Rafal Korlacki
University of Nebraska-Lincoln






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