[Wien] how to increase precision of calculations?

[Martin Gmitra]

Dear Wien2k users,

We are calculating spin-orbit coupling splitting of valence band in
wurtzite GaAs using mBJ. Since we are interested in a fine structure
close to Gamma point, we need to achieve sufficient accuracy. I am
attaching a plot of the valence band spin-orbit coupling splitting
(divided by the amplitude of k) as a function of k from the Gamma
point (k=0). As you can see, the splitting is sensitive to RKmax and
it does not look like it is going to "converge". What bothers me in
addition, is the step in the curves around 0.003 which can not be
healed by increasing RKmax (a smooth behavior as close as possible to
the Gamma point is desired result). I would like to add that
increasing k-mesh density does not affect the results as well as
increasing IFFT factor or reducing RMTs.

Do you have any suggestions?
Best regards,
Martin Gmitra
Uni Regensburg
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