[Wien] Plotting surface potential

Thu Dec 18 14:13:04 CET 2003

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?

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
---------------------------------

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