[Wien] problem with supercell

[Kevin Jorissen]

Hello Angelica,

I never did this myself, but I remember that it has been discussed on the
mailing list about a year ago (you can check the digest).  People asked
about using dummy atoms (i.e., empty spheres in your structure).  I remember
that P. Blaha was not really fond of this idea, but to those who persisted
in trying, he advised not to use a dummy atom with Z=0 during
initialization, but one with a small charge (eg. 1).  Then you would have to
correct this in case.struct (and also the number of electrons in case.in2, I
suppose) before starting the SCF.
I'm not sure how that might relate to your problems, but I thought I'd
mention it anyway.

About the calculation-that-takes-too-long : from the convergence (rkmax, nk)
of the simple material, you can make a good extrapolation for the number of
k-points necessary for the supercell.  See Stefaan's paper for details.


Good luck,

Kevin.

----- Original Message -----
From: "Yaron and Angelica" <strutza at bgumail.bgu.ac.il>
To: <wien at zeus.theochem.tuwien.ac.at>
Sent: Thursday, July 17, 2003 7:54 PM
Subject: [Wien] problem with supercell


> Hello WIEN users,
>
> I'm working with supercell of 16 atoms (unit cell FeAl b2) and it takes to
much time for
> process "x dstart" (initialization of the calc.) and for the SCF
> calc. How can I reduce the calculation time? I took 1000 k-mesh,
> maybe it is to much or there are some others parameters to consider.
>
>
> My second question about vacancy ball creation in this supercell.
> I took 15 atoms (without atom in the center of supercell) and the SCF
> stopped with error in lapw1 :
>
> 'INILPW' - can't open unit: 18
>  'INILPW' -        filename: FeAl-vb3.vsp
>  'INILPW' -          status: old          form: formatted
>  'LAPW1' - INILPW aborted unsuccessfully.
>
>
>  please advice.
>
>
>
>
> --
> Best regards,
> Angelica                          mailto:strutza at bgumail.bgu.ac.il
>
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