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Dear Dr. Blaha,<br>
<br>
Thank you very much for your reply. I have recalculated Cu(111) surface with
LDA and also with PBE96. LDA gives just perfect behavior for XC potential
around the surface. It is also very smooth in the vacuum region. Now it is
clear that the noise in vacuum which I talked about comes from the error
in GGA. PBE96 looks better than PW91, but it has some jump where Vxc reaches
0. I have to note that GGA oscillates even inside the slab. I attach to the
message a one-dimensional plotting which shows the Vxc along a certain line
normal to the surface for these three approximations.<br>
<br>
I use the version uploaded and installed in early September 2003. I don't
know if it is new. The case.clmsum files takes 5.3MB, so I decided to send
it to you, if you let me know that the version I use is new. Thanks again,<br>
<br>
Sergey Stolbov<br>
<br>
Peter Blaha wrote:<br>
<blockquote type="cite"
cite="midPine.LNX.4.44.0312180903420.16425-100000@susi.theochem.tuwien.ac.at">
<pre wrap="">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.
</pre>
<blockquote type="cite">
<pre wrap="">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
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</pre>
</blockquote>
<pre wrap=""><!---->
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: <a class="moz-txt-link-abbreviated" href="mailto:blaha@theochem.tuwien.ac.at">blaha@theochem.tuwien.ac.at</a> WWW: <a class="moz-txt-link-freetext" href="http://info.tuwien.ac.at/theochem/">http://info.tuwien.ac.at/theochem/</a>
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</pre>
</blockquote>
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