[Wien] about "c" in TB-mBJ for open structures

[tran at theochem.tuwien.ac.at]

Hi,

The mBJ potential can certainly not be used for systems with infinite
vacuum (e.g., isolated molecule, surface), but for open structures the
results can (maybe) still be ok without fixing "c" to some value
(I have not tried myself, but maybe there is already results in the
literature on open structures). If the gaps that you obtained without
fixing "c" are not completely wrong, then I do not see any reason
to fix "c" from a previous calculation.

Also, there is no reason to fix "c" to the one obtained with graphite
and not another solid. The procedure you mentioned looks ok.

F. Tran

On Thu, 15 Aug 2013, Fabiana Da Pieve wrote:

> Dear wien2k developers and users
>
> I am checking the performance of Tran-Blaha mBJ with respect to GW
> (non self consistent, for the moment) for some organic crystals (quite
> open structures). For some of them the improvement with respect to LDA
> (my starting point for G0W0) is good, for some others it is still
> pretty good but I would like to have a better result. Prof. Blaha
> suggested sometime ago to use the "c" parameter from bulk graphite,
> since the scf calculation  of the "c" parameter of TB-mBJ in suh open
> structures could have not so much sense.
>
> I am using Wien2k_11.1. Could you please confirm that the procedure I
> am going to use (reported here below) is correct ?
> (I just want a confirmation of what I read in the manual for this
> version at page 50,
> or IF THERE IS SOMETHING MORE THAT I SHOULD DO and that I did not
> catch from the manual).
>
> I will do a bulk calculation for graphite, then take the graphite.grr
> file, copy it into the orgcrystal.grr ; then I will cancel  the
> orgcrystal.in0_grr file and then I will run finally the mBJ self
> consistent run. The value inside the .grr file (which will be indeed
> the one corresponding to bulk graphite) will be read by the scf mBJ
> run.
>
> (sorry to ask, but my contract finishes soon and I cannot allow myself
> to do stupid errors...)
>
> Thank you very much
> Fabiana
>
> VUB, Free University of Brussels
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