[Wien] (no subject)

[Laurence Marks]

RKMAX is well described in the User Guide.

In general I don't hold the hands of people doing simple calculations such
as a GaN supercell, and I don't think other people will either -- unless
you want to pay?

Research involves working things out for yourself, and only asking the
harder questions as relevant.

On Tue, Mar 12, 2019 at 9:57 AM umbreenrasheed <umbreenrasheed at yahoo.com>
wrote:

> Thanks for your kind reply.
> I am trying to run GaN supercell with 12 parallel processors. But want to
> know about k points for this.
> Please also guide me about RTMAX
>
> -------- Original message --------
> From: Laurence Marks <L-marks at northwestern.edu>
> Date: 3/12/19 7:34 PM (GMT+05:00)
> To: A Mailing list for WIEN2k users <wien at zeus.theochem.tuwien.ac.at>
> Subject: Re: [Wien] (no subject)
>
> The number of k-points needed depends upon:
> a) Whether you are doing a pre-convergence, e.g. MSR1a or a final
> convergence.
> b) The size of the cell
> c) Whether you have a metal or an insulator (partially occupied states at
> E_F)
> d) The atomic number -- high Z can converge worse -- and whether you have
> d/f electrons.
>
> I would estimate that for a metal something like a k-point density of 50
> nm^3 is good for reasonable precision. Divide by 2-4 for an insulator,
> divide by 2-4 for pre-convergence and perhaps multiply by 2-4 for phonons
> or high precision.
>
> So long as memory is not an issue, you should try and divide the k-points
> across cores/nodes in an even fashion. It will also depend upon whether mpi
> or threading is better on your system, this seems to vary. It is hard to
> make clean statements without more information.
>
> For a small problem (e.g. RKM=200-500) I would tend to distribute with 1-2
> cores per k-point, e.g. use
> 1:node1
> 1:node1
> 1:node1
> 1:node1
>
> In .machines. (Add a :2 after the node1 to use mpi.) For a larger problem
> (e.g. RKM+12000) you probably want to just run one process. For a very
> large problem, e.g. RKM=30000 -- get access to a larger cluster!
>
> Experiment.
>
>
> On Tue, Mar 12, 2019 at 8:34 AM umbreenrasheed <umbreenrasheed at yahoo.com>
> wrote:
>
>> How many k points should be selected for 8 parallel processors selection
>> in wein2k..
>> What is general relation between the two?
>>
>
>
> --
> Professor Laurence Marks
> "Research is to see what everybody else has seen, and to think what nobody
> else has thought", Albert Szent-Gyorgi
> www.numis.northwestern.edu ; Corrosion in 4D:
> MURI4D.numis.northwestern.edu
> Partner of the CFW 100% program for gender equity, www.cfw.org/100-percent
> <https://urldefense.proofpoint.com/v2/url?u=http-3A__www.cfw.org_100-2Dpercent&d=DwMGaQ&c=yHlS04HhBraes5BQ9ueu5zKhE7rtNXt_d012z2PA6ws&r=U_T4PL6jwANfAy4rnxTj8IUxm818jnvqKFdqWLwmqg0&m=KScdO-7lyX_mw6Eoehq4OKL6k9Q-BUJMbO0pizP1iCY&s=Mw8WSKEEH1kbDakoqWq_PysInzFGvfLDl98Gbafpd7Q&e=>
> Co-Editor, Acta Cryst A
>


-- 
Professor Laurence Marks
"Research is to see what everybody else has seen, and to think what nobody
else has thought", Albert Szent-Gyorgi
www.numis.northwestern.edu ; Corrosion in 4D: MURI4D.numis.northwestern.edu
Partner of the CFW 100% program for gender equity, www.cfw.org/100-percent
Co-Editor, Acta Cryst A
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