[Wien] the error of "semicore band ranges too large" and NMR calculations

[Peter Blaha]

This new test (v 13.1) checks for ghostbands, which otherwise would go
through without notice. I consider it a VERY important check and in
almost all cases it is a severe problem.

It has the same origin as the STOP due to "QTL-B too large", namely
unphysical ghostbands.

Ghostbands occure for two reasons:
a) the energy parameters are not set properly. This means most of the time
    that the wien2k-defaults for your system (mainly due to the required RMT
    values or due to a particular charge transfer) are not good. In most cases
    it comes because for ONE atoms there are 2 expansion energies for the same "l",
    and these energies are too close.
b) The sphere sizes are too different. This happens in particular when a cation
    (like your Na or Ca) has too large spheres compared to H, O, B. Often such
    ghostbands appear for (partly) converged calculations.

Thus for your case, I suggest you reduce your large spheres (Na, Ca ??) by eg.
0.3 bohr (I can't  be more specific since I don't know any details).


Am 05.12.2013 06:51, schrieb Bing Zhou:
> Dear all,
> "LAPW2: semicore band-ranges too large, possible ghost band" occurred at the 15th SCF for the mineral
ulexite (NaCa[B5O7(OH)4]H2O), so my question is: does such an error will affect the NMR calculations for this mineral?
> Best wishes,
> Bing
>
>
> --------------------------------------------
> On Wed, 12/4/13, tran at theochem.tuwien.ac.at <tran at theochem.tuwien.ac.at> wrote:
>
>   Subject: Re: [Wien] semicore band ranges too large error
>   To: "A Mailing list for WIEN2k users" <wien at zeus.theochem.tuwien.ac.at>
>   Received: Wednesday, December 4, 2013, 3:08 PM
>
>   This check was introduced recently to
>   detect ghost bands.
>   If this problem appears at the very beginning of the SCF
>   iteration
>   for a new geometry then there is probably no problem of
>   ghost bands.
>   This is just the starting density which is not good.
>
>   To avoid the stop of the calculation, in case.in2 set the
>   value of
>   iqtlsave to 0.
>
>   F. Tran
>
>
>   On Wed, 4 Dec 2013, Torsten Weissbach wrote:
>
>   > Dear all,
>   >
>   > after switching to Wien2k_13, I frequently get the
>   "semicore band ranges
>   > too large" error, often during relaxation. Though I can
>   understand why
>   > that should not happen, can you explain what could have
>   gone wrong that
>   > it appears and how the source of this error can be
>   traced?
>   >
>   > Best regards,
>   > Torsten
>   >
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-- 
-----------------------------------------
Peter Blaha
Inst. Materials Chemistry, TU Vienna
Getreidemarkt 9, A-1060 Vienna, Austria
Tel: +43-1-5880115671
Fax: +43-1-5880115698
email: pblaha at theochem.tuwien.ac.at
-----------------------------------------