[QE-users] Relativistic momentum operator

[Thomas Brumme]

Dear all,

I want to approximately calculate the g factor of excitons from the DFT 
band structure as described in this PRB:

https://journals.aps.org/prb/abstract/10.1103/PhysRevB.101.235408

and for this I essentially need the momentum-matrix elements. I already 
found that I can calculate the matrix elements of the velocity operator 
and I modified write_p_avg.f90 to have access to all elements and not 
only those between the valence and conduction bands. Yet, before 
implementing something more solid, I noticed that I also need the 
relativistic momentum as shown in Eq. (9) of the above paper. The 
additional term due to spin-orbit coupling seems not to be included in 
the calculation in compute_ppsi.f90 or is this also included in the 
non-local part of the pseudo-potential? If this is the case, everything 
is fine :) However, if this is not included, does anyone have an idea if 
something like this is already included somewhere in the code maybe in 
the DFPT/phonon code?

Kind regards

Thomas

-- 
Dr. rer. nat. Thomas Brumme
Theoretical chemistry
TU Dresden - KOE / 103
Bergstr. 66c
01069 Dresden

Tel:  +49 (0)351 463 39449

email: thomas.brumme at tu-dresden.de