[DFTB-Plus-User] surface slab calculation don't converge

[Bálint Aradi]

Dear malahmer,

> thank you for your help
> however i don't understand what you mean by equivalent surfaces, since in my input there is to polar surfaces the O-termined and Zn-termined surface and only the later was passivated by hydrogen atoms. the o surface can't passivated by H atoms because the goal of my calculations is to study the interaction of H atoms with these surface.

I guess what Sascha means, is that usually, it is more fortunate to have
twice the same surface, both passivated with the atoms you would like to
study (H in your case, I guess). Having a "naked" surface on one side
and a passivated one on the other side could lead to serious problems.

> i also would ask if DFTB+ use a jullium background to compensate the charged system as in other codes

It does, but your system was neutral, so it should not change things.

Anyway, using the following Hamiltonian, I managed to get your surface
converged. Whether it converges to a reasonable state I did not check,
that would be your job:

Hamiltonian = DFTB {
 SCC = Yes
 SCCTolerance = 1.000000000000000E-003
 MaxSCCIterations = 300
 #EwaldParameter = 0.02
 MaxAngularMomentum = {
  Zn = "d"
   O = "p"
   H = "s"
 }
 Charge = 0

 Eigensolver = DivideAndConquer {}

 Filling = Fermi {
   Temperature [Kelvin] = 1000.0
 }
 SlaterKosterFiles = Type2FileNames {
   Prefix = "./slakos/"
   Suffix = ".skf"
   Separator = "-"
 }
 KPointsAndWeights = SupercellFolding{
  6    0   0
  0    8   0
  0    0   1
 0.5  0.5 0.0
 }
 }

Notes: I've set a much higher filling temperature, as there was clearly
some charge oscillations going on in your system.

I've set an odd MP-scheme, which gives usually better average.

I've removed the options to Broyden, in order to use the defaults, which
are good enough for most cases.


  Best regards,

  Bálint


Ps. Do not use WriteAutotest = Yes, unless you want to use it within the
autotest feature (which probably do not).


-- 
Dr. Bálint Aradi
Bremen Center for Computational Materials Science, University of Bremen
http://www.bccms.uni-bremen.de/cms/people/b_aradi/


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