[Wien] mBJ potential for molecules?

[Peter Blaha]

mBJ was designed for solids and it could well be that for a molecules the procedure
to determine a proper "c"-value (average of grad rho/rho) does not work and you get
unphysical values due to the vacuum region.

In such a case I can only recommend to remove case.in0_grr, and set
a proper grad rho/rho value in case.grr yourself.

A good estimate would be to set it to a similar value as a "similar" bulk-system
(eg. diamond) would have.

Also: Make sure you modified case.inm and set PRATT mixing !

Ricardo Faccio schrieb:
> Dear users
> 
> I've been working on the isolated molecule catechol 
> (http://en.wikipedia.org/wiki/Catechol) in order to see how mBJ affects 
> its HOMO-LUMO gap.
> 
> The initialization and convergence at GGA-PBE level went fine, obtaining 
> a energy gap of 4.0 eV in concordance with other DFT codes.
> 
> Afther this I proceeded in order to incorporate the modified 
> Becke-Johnson potential (MBJ), but I found several problems in 
> determining the position of the Fermi level. What we see is a clear 
> problem of finding enough eigenvalues, which arelower than the number of 
> valence electrons. Therefore we proceed according to the userguide by:
> -changing the Fermi-Method (tetra, gauss and temp) -> error persist
> - changing Rmt to similar values increasing the lmax to12 -> error persist
> - increasing energy window in case.klist  and case.in1c in order to 
> catch the lost eigenvalues -> error persist
> It seems to be a problem on a big change introduced by the mBJ potential 
> which induces important divergences iat the  lapw1.
> 
> ######################
> 
> case.output1up 
> 
> ###################### 
> 
>     EIGENVALUES ARE:
>       1.4443359    1.4892578    1.8037109    1.8486328    1.8486328
>       1.8935547    1.9384766    1.9384766
>          1923 EIGENVALUES BELOW THE ENERGY   -9.00000
>        ********************************************************
> The problem always occurs in the first cycle of the mBJ procedure after 
> lapw1, with few eigenvalues as you can see.
> 
> I succeed applying this methodology to bulk systems such as TiO2.
> 
> Any suggestion?
> 
> Best regards
> 
> Ricardo
> 
>  
> 
> -------------------------------------------------------------------------
>   Dr. Ricardo Faccio
>   Prof. Adjunto de Física
>   Mail: Cryssmat-Lab., Cátedra de Física, DETEMA
>   Facultad de Química, Universidad de la República
>        Av. Gral. Flores 2124, C.C. 1157
>        C.P. 11800, Montevideo, Uruguay.
>   E-mail: rfaccio at fq.edu.uy <mailto:rfaccio at fq.edu.uy>
>   Phone: 598 2 924 98 59
>               598 2 929 06 48
>   Fax:    598 2 9241906
>   Web:  http://cryssmat.fq.edu.uy/ricardo/ricardo.htm
> ---------------------------------------------------------------------------------
> 
> 
> ------------------------------------------------------------------------
> 
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-- 

                                       P.Blaha
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Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
Phone: +43-1-58801-15671             FAX: +43-1-58801-15698
Email: blaha at theochem.tuwien.ac.at    WWW: http://info.tuwien.ac.at/theochem/
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