[Wien] Plotting surface potential

Thu Dec 18 15:27:47 CET 2003

Marco Schowalter wrote:
> Dear Dr. Stolbov, dear Prof. Blaha,
> 
> I use the same routines (lapw0 and lapw5) as Dr. Stolbov to calculate 
> the coulomb potential of semiconductors on . I am using WIEN2k_03 
> (Release 18/01/2003) and I can hardly imagine  that such a feature is 
> present in my version. However I want to check this. So Dr. Stolbov, 
> could you please send me your struct file, the picture of the groove and 
> maybe the corresponding in5 file. If I have understand it right, what 
> you wrote, I should see an effect when I average the coulomb potential 
> in slices perpendicular to the slab direction. But this is not the case 
> for me (see attachment, the y-axis shows the distance in Angstroem). So 
> that would mean that there is no problem in the scf in my version. 
> Please correct me when I am wrong
> 
> Prof. Blaha, what do you mean with the "printing of vcoul does not work 
> any more"? Is there only a change of the format or are there wrong 
> numbers in vcoul?

Sorry Dr. Stolbov, Prof. Prof. Blaha,

I was a little bit too fast with my email. I do not use exactly the same 
command as Dr. Stolbov. I use "x lapw -c" instead of  "x lapw -p -c" and 
if I have understand you now right this is an essential diffrence.

Best regards

Marco Schowalter

> 
> Dr. Stolbov, did you change TOT to COUL in the in0 file ? Because I only 
> get the coulomb potential in vcoul if I have changed this before in in0.
> 
> 
> Best regards
> 
> Marco Schowalter
> 
> 
> 
> 
>  >Hi,
>  >
>  >The problem you report is most likely NOT due to your fault and 
>  >unfortunately
>  >it is also present in the scf cycle.
>  >
>  >What version of WIEN are you using ?
>  >
>  >In LDA the problems should be smaller.
>  >
>  >In GGA we have to use various cutoffs (for the density and for the 
>  >gradients)
>  >and after some tests made by some WIEN-user, those limits were set 
> (now >to
>  >fairly small values and I could imagine they are too small). I
>  >could imagine that for very small densities the numerical gradients 
>  >might be
>  >huge and than such unphysical XC-potential could arise due to not well
>  >chosen cutoffs.
>  >
>  >I need to check this in detail. When you are using the latest WIEN2k 
>  >version,
>  >please send struct and clmsum file to my personal email adress (not the
>  >WIEN-mailing list), otherwise try the latest version.
>  >
>  >PS: I checked it and can see that the printing of vcoul does not work 
>  >anymore.
>  >It seems to happen during parallelization of lapw0. I'll fix this too.
>  >
>  >> I have a problem plotting the potential of metal surfaces. When I 
>  >>plot
>  >> it, say for Cu(111) surface, I see a groove like feature parallel to 
>  >>the
>  >> surface located somewhere at the barrier region. The depth of that
>  >> groove is 0.2Ry!!! and the width is about 2 angstroms.   I found 
> that >>it
>  >> comes from the exchange correlation part of potential that looks 
>  >>totally
>  >> unphysical, because the charge density in that region behaves
>  >> reasonably, namely decays exponentially and is very low. The feature 
>  >>is
>  >> stable with respect to a change in Gmax and/or RKM.  Even if I 
>  >>increase
>  >> Gmax from 14 to 40 and RKM from 7 to 9.5, it remains the same. I 
>  >>cannot
>  >> attach the picture to the message, because the file size is about 600
>  >> kB. If someone is interested in, I can send it to his/her personal 
>  >>address.
>  >>
>  >> First, I would like to understand if this feature is a result of my
>  >> misuse of the lapw5, or some bug in lapw5, or (that would be too 
> bad) >>it
>  >> appears in SCF calculations. Of course, in case of  the clean Cu 
>  >>surface
>  >> the barrier is high and I guess this feature does not affect the
>  >> occupied states to much, but when I put alkali metal on it, the work
>  >> function is significantly reduced and that feature could give me 
>  >>"very
>  >> very interesting" effects. Could anyone help me to solve this 
>  >>problem?
>  >>
>  >> Another question is about oscillations of potential in the vacuum
>  >> region. They do decrease when I increase Gmax. But what is amusing,
>  >> charge density is very smooth even at smaller values of Gmax and RKM.
>  >>
>  >> Now, let me show you haw I do it.
>  >>
>  >> x lapw0 -p -c  (with R2V in case.in0)
>  >> x lapw5 -c (to create lapw5.def)
>  >> replace case.clmval with case.r2v (or case.vcoul) in lapw5.def
>  >> lapw5 lapw5.def
>  >>
>  >> By the way, I found in the manual, that case.vcoul should comprise of
>  >> both total and Coulomb potentials, but it looks like it contains only
>  >> total one.
>  >>
>  >> Thank you in advance for your suggestions,
>  >>
>  >> Sergey Stolbov
>  >>
>  >> _______________________________________________
>  > Wien mailing list
>  > Wien at zeus.theochem.tuwien.ac.at
>  > http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien
>  >
> 
> 
>                                       P.Blaha
> --------------------------------------------------------------------------
> 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/
> --------------------------------------------------------------------------
> 
> 
> 
> 

-- 
---------------------------------
Dr. Marco Schowalter
Theoretical Study of Matter
Department of Physics
University of Antwerpen
Groenenborgerlaan 171
2020 Antwerpen
BELGIUM
Tel: +32-(0)3-2653-316
Fax: +32-(0)3-2653-318
email: Marco.Schowalter at ua.ac.be
---------------------------------