[Wien] how to increase precision of calculations?

[tran at theochem.tuwien.ac.at]

Actually, the most important is maybe the number of bands calculated
by lapw1 which are used for the 2nd variational procedure for the
spin-orbit coupling. So, to increase Emax in case.in1 (up to 20 Ry or even
more) should be tried.

F. Tran

On Sat, 29 Nov 2014, tran at theochem.tuwien.ac.at wrote:

> Hi,
> For the convergence, I suggest to increase RKmax further. RKmax=8 is
> (very) good, but also not fully converged usually. Going up to
> RKmax=10 makes sense.
>
> It's difficult to say for the step at 0.003. Maybe the k-mesh is still
> not dense enough. An increase of GMAX (12 -> 18) in case.in2 is worth to
> try.
>
> F. Tran
>
> On Sat, 29 Nov 2014, Martin Gmitra wrote:
>
>> 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
>> 
>