[Wien] how to increase precision of calculations?

[Peter Blaha]

Could you please send me your struct file, the k-mesh around Gamma and 
some indications which band splitting you are looking up to my private 
email.
I want to cross check this as it looks rather uncommon to me.

On 12/01/2014 08:10 AM, Martin Gmitra wrote:
> Hi Fabien,
>
> Thanks for your reply and suggestions. I went with RKmax up to 12Ry
> and it turned out that 11 and 12 should be okay, since the splitting
> starts to "oscillate" (change in the increasing trend with increased
> RKmax). Concerning the non smooth behavior of the curve I did several
> test calculations playing around with the input parameters and none of
> the changes have brought desired healing of the step close to 0.003. I
> am attaching plots to the attachment.
>
> If there are any hints, please let me know.
> Best regards,
> Martin Gmitra
> Uni Regensburg
>
>
> On Sun, Nov 30, 2014 at 12:02 AM,  <tran at theochem.tuwien.ac.at> wrote:
>> 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
>>>>
>>>
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-- 

                                       P.Blaha
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Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
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Email: blaha at theochem.tuwien.ac.at    WIEN2k: http://www.wien2k.at
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