[Wien] Improving k-mesh/RKMAX etc

[shamik chakrabarti]

Dear Prof. Marks,

                     Thanks for your elaborations. These will be helpful.

with regards,

On Mon, 9 Aug 2021 at 19:25, Laurence Marks <laurence.marks at gmail.com>
wrote:

> This type of question has come up many times, so let me expand/clarify
> what Peter said.
>
> In general, you can optimize positions and converge the density using a
> smaller number of k-points and also a smaller RKMAX. You then save this
> density and improve both the k-points and RKMAX, and sometimes also the
> RMTs (using reduce_rmt_lapw with the "-a" option). In most cases the forces
> only change by a few mRyd/au. While the energy and how much of the density
> is within the RMTs will change, normally it will converge in these
> "improved" runs in a small (5-10) number of iterations. This is much less
> than the 20-50 that are normally required to converge from atomic densities
> [1].
>
> The reason that Peter recommended saving the prior run is just in case
> something goes wrong. (Even experienced useres sometimes mess up!)
>
> [1] If you need more than 50 iterations to converge just the densities
> (fixed positions), you may have something wrong with your model.
>
> On Mon, Aug 9, 2021 at 8:22 AM Peter Blaha <pblaha at theochem.tuwien.ac.at>
> wrote:
>
>> What do you mean by "can I wait for scf convergence with 4 k-points in a
>> new folder ????
>>
>> Even in a new folder:   NEVER do an   init_lapw
>> again, but always use the previous saved files.
>>
>> mkdir new
>> cd new
>> cp ../relaxed_4k-points.* .
>> restore relaxed_4k-points
>>
>> x kgen    with better k-mesh
>>
>> runsp_lapw ...
>>
>>
>> -------- Weitergeleitete Nachricht --------
>> Betreff:        Query about denser k-mesh for calculating more accurate
>> total
>> energy/unit cell
>> Datum:  Mon, 9 Aug 2021 17:58:13 +0530
>> Von:    shamik chakrabarti <shamik15041981 at gmail.com>
>> An:     pblaha at theochem.tuwien.ac.at
>>
>>
>>
>> Dear Prof. Blaha,
>>                                As has been discussed in the wien2k
>> mailing list I am following your advice regarding the structure
>> optimization & steps to be followed after runsp_lapw -fc 1.0 -ec 0.0001
>> -cc 0.0001 -min.
>>
>>    save_lapw relaxed_4k-points   (if not already done)
>> x kgen   with as many k-points as you want.
>> runsp ...   (first without -min, because most likely the forces will not
>> change with the bigger k-mesh).  --
>>
>> Here I have a query. Can I wait till the convergence is achieved with 4
>> k points (during total energy calculation in a new folder)& then (after
>> convergence with 4 k points) increase the k-points to 14 k points?
>>
>> with regards,
>>
>> Dr. Shamik Chakrabarti
>> Research Fellow
>> Department of Physics
>> Indian Institute of Technology Patna
>> Bihta-801103
>> Patna
>> Bihar, India
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>>
>
>
> --
> Professor Laurence Marks
> Department of Materials Science and Engineering
> Northwestern University
> www.numis.northwestern.edu
> "Research is to see what everybody else has seen, and to think what nobody
> else has thought" Albert Szent-Györgyi
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-- 
Dr. Shamik Chakrabarti
Research Fellow
Department of Physics
Indian Institute of Technology Patna
Bihta-801103
Patna
Bihar, India
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