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<p>Luis, look for Hubbard Model</p>
<p>NaCl U2</p>
<p> Pablo<br>
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<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>De:</b> Wien <wien-bounces@zeus.theochem.tuwien.ac.at> en nombre de Luis Ogando <lcodacal@gmail.com><br>
<b>Enviado:</b> lunes, 21 de noviembre de 2016 11:00:23 a. m.<br>
<b>Para:</b> A Mailing list for WIEN2k users<br>
<b>Asunto:</b> Re: [Wien] Hartree-Fock and the Hubbard Model</font>
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<div>Dear Prof. Tran,<br>
<br>
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I would like to read more about this subject, but, unfortunately, your link gave me a message like : " Wikipedia does not have an article with this exact name. "<br>
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<div> Please<b>,</b> could you suggest another non-specialist reference like wikipedia ?<br>
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<div> Thank you,<br>
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<div> Luis<br>
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<div><b></b></div>
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<div class="gmail_extra"><br>
<div class="gmail_quote">2016-11-20 13:28 GMT-02:00 <span dir="ltr"><<a href="mailto:tran@theochem.tuwien.ac.at" target="_blank">tran@theochem.tuwien.ac.at</a>></span>:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
Hi,<br>
<br>
DFT+U is a cheap but rather rough approximation of HF.<br>
Beside this, there is also the difference that in DFT+U, the Coulomb<br>
operator is attenuated in order to account for the screening due to<br>
correlation. In HF, no correlation is included.<br>
In hybrids, the screening is included by using only ~25% of HF exchange<br>
(and there is also correlation coming from a LDA/GGA correlation term).<br>
<br>
Hybrid, onsite-hybrid and DFT+U are more or less the same,<br>
since all of them are one-electron methods and mix HF with LDA/GGA.<br>
As Karel said, they are better than LDA/GGA, but can not reproduce<br>
the experimental observations that are beyond the one-electron methods.<br>
DMFT is better since it is a beyond one-electrons method.<br>
<br>
Read that:<br>
<a href="https://en.wikipedia.org/wiki/LDA+U" rel="noreferrer" target="_blank">https://en.wikipedia.org/wiki/<wbr>LDA+U</a><br>
<br>
FT
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<div class="h5"><br>
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<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
On Wed, 16 Nov 2016, delamora wrote:<br>
<br>
<br>
Dear Fabien Tran and Karel Vyborny,<br>
<br>
Thanks for your comments.<br>
<br>
<br>
What I want to know is if the Hartree Fock exchange is what the Hubbard U is<br>
trying to model<br>
<br>
What I know is that for strong intraatomic repulsion, 3d and 4f, the Hubbard<br>
U gives good results, although the U is a parameter.<br>
<br>
But for intermediate intraatomic repulsion, 4d, 5d, 5f then more expensive<br>
methods are needed, such as DMFT<br>
<br>
So, if this is the case that the Hartree Fock exchange is what the Hubbard U<br>
is trying to model then the hybrid functionals would do a better job.<br>
<br>
So, my question is; What are the Hubbard U and DMFT trying to model?<br>
<br>
<br>
Cheers<br>
<br>
Pablo de la Mora</blockquote>
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