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<p style="margin-top:0;margin-bottom:0">I strongly disagree</p>
<p style="margin-top:0;margin-bottom:0">Wikipedia gives a very different definition<br>
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<p style="margin-top:0;margin-bottom:0"><a href="https://en.wikipedia.org/wiki/Semimetal" class="OWAAutoLink" id="LPlnk966700" previewremoved="true">https://en.wikipedia.org/wiki/Semimetal</a><br>
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Bi would be a good example; it has a very low DOS at Ef (with the wikipedia definition of semimetal)<br>
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Graphite is conductor in the ab plane and a poor conductor (not insulating) in the c direction</div>
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As I said, the bands are flat near the band edge, so it would be a bad conductor (does this fall into the definition of semimetal???)</div>
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Flat bands give high DOS? Not always, for example NaCl at the bottom of the conduction band, the band is flat and DOS is very low</div>
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And I do not think I need a high density of k points<br>
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On the other hand the f orbitals have flat bands and DO HAVE high DOS<br>
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<div id="divRplyFwdMsg" dir="ltr"><font style="font-size:11pt" color="#000000" face="Calibri, sans-serif"><b>De:</b> Wien <wien-bounces@zeus.theochem.tuwien.ac.at> en nombre de Fecher, Gerhard <fecher@uni-mainz.de><br>
<b>Enviado:</b> martes, 29 de enero de 2019 03:49 a. m.<br>
<b>Para:</b> A Mailing list for WIEN2k users<br>
<b>Asunto:</b> Re: [Wien] Metal or semimetal</font>
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<div class="PlainText">I strongly disagree,<br>
a semi-metal (not to be confused with a half-metall) is a material that is insulating (semiconducting) in one direction and conducting in another one, a typical example is graphite.<br>
(this has nothing to do whether the bands are flat or not;<br>
and just to mention, the density of states is HIGH when the bands are FLAT.)<br>
<br>
The question is: What is slightly below ?<br>
<br>
If you have one (or more) partially filled band(s) that is(are) crossing the Fermi energy, then you have a metal.<br>
(You find the occupation of the bands e.g.: in case.scf2)<br>
<br>
If you have not enough k-points (or some other bad conditions), then the integration of the density of states might be bad<br>
and the Fermi energy may fall into the valence or conduction band (probably few meV or less) even though the material is an insulator,<br>
this can be healed in most cases by increasing the number of k-points.<br>
<br>
In some cases you have to check whether there might be an overlapp of the valence and and conduction bands at different k-points, resulting in a semimetallic or zero-bandgap type behavior.<br>
For example you may have a large gap at Gamma with EF at the top of the valence band and a large gap at another k-point, say X, with EF at the bottom of the conduction band.<br>
<br>
PS.: To complete; in a half-metal one spin channel (e.g. minority) is insulating (semiconducting) and the other spin channel is metallic (e.g.: majority)<br>
<br>
<br>
<br>
Ciao<br>
Gerhard<br>
<br>
DEEP THOUGHT in D. Adams; Hitchhikers Guide to the Galaxy:<br>
"I think the problem, to be quite honest with you,<br>
is that you have never actually known what the question is."<br>
<br>
====================================<br>
Dr. Gerhard H. Fecher<br>
Institut of Inorganic and Analytical Chemistry<br>
Johannes Gutenberg - University<br>
55099 Mainz<br>
and<br>
Max Planck Institute for Chemical Physics of Solids<br>
01187 Dresden<br>
________________________________________<br>
Von: Wien [wien-bounces@zeus.theochem.tuwien.ac.at] im Auftrag von delamora [delamora@unam.mx]<br>
Gesendet: Freitag, 25. Januar 2019 01:53<br>
An: A Mailing list for WIEN2k users<br>
Betreff: Re: [Wien] Metal or semimetal<br>
<br>
If Ef is near the edge of a band, close to the bandgap then it would be a bad conductor, since the bands would be quite flat (and the velocity of the electrons is proportional to the slope of the band) and the DOS would be low, so I would call it a semimetal<br>
<br>
<br>
________________________________<br>
<br>
Dear wien2k users:<br>
<br>
I have a question that does not have any relation with wien2k but I would be grateful if you can answer me or send me a document:<br>
<br>
When the fermi level passes slightly below the top of the valance band with the presence of a wide gap, this indicates a metal or semimetalic behavior.?<br>
<br>
Thank you in advance<br>
_______________________________________________<br>
Wien mailing list<br>
Wien@zeus.theochem.tuwien.ac.at<br>
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