[Wien] surface calculations convergence

[Peter Blaha]

>  I am a fairly new user of the Wien2k code trying out
> some
> calculations of surface.
> First of all I choose  the following parameters :
> 9kpoint, Rkmax=7,
> Gmax=14. Gradually I increased the vacuum region and I
> get the
> follwing results :



ELS_POTZ(0;0.5)=0.29376; 0.29376)

I don't quite understand how the potential could be the same at z=0 and z=0.5
These two values are there, since some slabs might be set-up with atoms around
0 (and the middle of the vacuum at 0.5), or the other way around).



a) the absolute value of the potential at the vacuum will always vary.
What is important is the workfunction is ELS-pot - Efermi
                                                           workfunction

> vacuum=18 Bohr->(ERy=-34203.340100, EFermi=-0.01240,         .306
> ELS_POTZ(0;0.5)=0.29376; 0.29376)
> vacuum=20 Bohr->(ERy=-34203.397248, EFermi=-0.04518,         .327
> ELS_POTZ(0;0.5)=0.28243; 0.28243)
> vacuum=22 Bohr->(ERy=-34203.365672, EFermi=-0.06347,         .335
> ELS_POTZ(0;0.5)=0.27183; 0.27183)
> vacuum=24 Bohr->(ERy=-34203.275210, EFermi=-0.08632,         .348
> ELS_POTZ(0;0.5)=0.26200; 0.26200)
> vacuum=26 Bohr->(ERy=-34203.151402, EFermi=-0.09458,         .347
> ELS_POTZ(0;0.5)=0.25277; 0.25277)
> vacuum=30 Bohr->(ERy=-34202.840131, EFermi=-0.10152,         .338
> ELS_POTZ(0;0.5)=0.23607; 0.23607)
> vacuum=32 Bohr->(ERy=-34202.677126, EFermi=-0.10785,         .336
> ELS_POTZ(0;0.5)=0.22849; 0.22849)

It is not really monotonic, but with some maximum. I'd expect a problem,
see below.



a) Etot decreases from 20 bohr on significantly (18 seems an exception)
   Usually the matrixsize should increase (at constant RKM
   use   grepline :RKM '*scf' 1      RKM constant, NMAT increases ?
   and   grepline :ENE '*scf' 1      and WARN ??

   2 explanations: i) Maybe NMATMAX got too small and your bases gets limited
                   when the vacuum increases
                   ii) Increase RKMAX




                                      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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