<div dir="auto"><div>I think you have misunderstood the code. The lcore -up uses the "up" potential, similarly for the "dn". That only 1/2 occupancies are used is just book-keeping in order to not have a different code for spin-polarized and non-polarized calculations.</div><div dir="auto"><br></div><div dir="auto">As an aside, I don't trust +U for 4f as it puts them inappropriately low in energy. You can look at both DOI: 10.1103/PhysRevMaterials.2.025001 & 10.1021/acs.inorgchem.2c04107 . The experimental valence XPS data from many authors is very clear that the energy of the 4f states is in the valence regime, at least in oxides. Just my opinion.<br><br><div data-smartmail="gmail_signature" dir="auto">--<br>Professor Laurence Marks (Laurie)<br>Department of Materials Science and Engineering, Northwestern University<br><a href="http://www.numis.northwestern.edu" target="_blank" rel="noreferrer">www.numis.northwestern.edu</a><br>"Research is to see what everybody else has seen, and to think what nobody else has thought" Albert Szent-Györgyi</div><br><div class="gmail_quote" dir="auto"><div dir="ltr" class="gmail_attr">On Mon, Jul 17, 2023, 06:51 Jindrich Kolorenc <<a href="mailto:kolorenc@fzu.cz" target="_blank" rel="noreferrer">kolorenc@fzu.cz</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Dear Wien2k developers and users,<br>
<br>
I would be grateful for your opinion, clarification or pointers to<br>
literature about core states in Wien2k or LAPW in general. My<br>
message is a bit long, I am sorry for that.<br>
<br>
It seems to me that there is some inconsistency in the way Wien2k<br>
treats the core states in spin-polarized calculations. As far as I<br>
understand it, LCORE is run twice, once for spin-up potential and<br>
once for spin-down potential. In each of these runs, the core states<br>
are full (up and dn occupied). Then, I suppose, the up charge density<br>
is set to 1/2 of the LCORE charge run for the up potential and dn<br>
charge density is set to 1/2 of the LCORE charge run for the dn<br>
potential. That is different than running a core solver once, each spin<br>
channel feeling its own potential, which would seem to me as a more<br>
"rigorous" strategy (but one could not use the same quantum numbers<br>
for the core states as LCORE does).<br>
<br>
I suppose that different approaches to the core states have some effect<br>
also on the total-energy expression, since it contains sum of<br>
eigenvalues (I suppose since mixer reads them from case.scf). In<br>
Wien2k, there are two eigenvalues for each core state for<br>
spin-polarized calculations. I checked Elk, and if I understand its<br>
output correctly, it lists only one eigenvalue for each core state for<br>
spin-polarized calculations. That probably means, that Elk runs one<br>
core calculation for an averaged potential (though I did not<br>
investigate Elk in detail to know for sure).<br>
<br>
Do you know about any book or paper where different strategies would<br>
be discussed and/or tested/compared? My LAPW reference, the David<br>
Singh's book, does not appear to touch this.<br>
<br>
It may well be that for full core states all this is usually<br>
negligible, but I am more concerned about consequences for the<br>
open-core approximation for 4f states (which is where I actually<br>
noticed this "issue")<br>
<br>
<a href="http://www.wien2k.at/reg_user/faq/open_core.html" rel="noreferrer noreferrer noreferrer" target="_blank">http://www.wien2k.at/reg_user/faq/open_core.html</a><br>
<br>
The FAQ entry does not mention spin-polarized calculations, but runsp<br>
does look for case.inc[up,dn] and it will use them if they exist. Then,<br>
fully spin-polarized polarized f^7 state is calculated as 1/2 (I<br>
suppose) of f^14 state, for instance. That is likely a good<br>
approximation for Eu^2+ charge density (full shell vs full subshell),<br>
but the eigenvalues/total energy are less obvious. And accuracy of<br>
approximating fully spin-polarized f^6 with 1/2 of spin-restricted f^12<br>
is even less obvious even for the charge density.<br>
<br>
I see that the FAQ entry says that one should use LDA+U instead of open<br>
core, but it has its own set of problems when applied to localized 4f<br>
too. And open core has one attractive feature for me - it gives an<br>
easy way to do calculations with constrained number of 4f electrons. Do<br>
you think it is meaningful to compare total energies for such<br>
calculations with different number of 4f electrons (charge-neutral<br>
cells, electrons shuffled between 4f and valence s,p,d).<br>
<br>
Any comments welcome.<br>
<br>
Best regards,<br>
Jindrich<br>
<br>
<br>
<br>
<br>
<br>
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