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<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>If you start with U = 0, the original s-conduction
band lies much lower than -0.3 eV, in fact it also lies below the split-off
band at around -1 eV. So the flipping has already taken place. The bands you
see combining at the top of the valence band are the flipped light hole band
and the heavy hole band. These are combining because they are forced to do so
by symmetry at k=0. Applying LDA+U to the Hg 5d orbitals will push the 5d
levels down and force the s-conduction band up towards the level -0.3 eV. If
you increase U from 0 it does not seem that much is happening at the valence
band top until the s-conduction band has risen to approach the valence band
top. If you set Ueff somewhere around 7.8 eV, the s-conduction band will touch
the degenerate heavy- and light hole bands at k=0, and if you rise U further,
you can even see the s-conduction band rising above the valence band edge to
give an ordinary band structure with a positive gap, and the light hole band
will then flip down to its “normal” non-inverted position. Thus, an Ueff
somewhat less than 7.8 eV on the Hg 5 d’s will give you the -0.3 eV band gap. <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Note however, that (mis)using LDA+U in
this way is fitting, and certainly not an ab-initio procedure, so avoid doing volume
optimization this way.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Trond Brudevoll<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
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<p class=MsoNormal><b><font size=2 face=Tahoma><span style='font-size:10.0pt;
font-family:Tahoma;font-weight:bold'>Fra:</span></font></b><font size=2
face=Tahoma><span style='font-size:10.0pt;font-family:Tahoma'> wien-bounces@zeus.theochem.tuwien.ac.at
[mailto:wien-bounces@zeus.theochem.tuwien.ac.at] <b><span style='font-weight:
bold'>På vegne av</span></b> ? ?<br>
<b><span style='font-weight:bold'>Sendt:</span></b> 17. oktober 2006 13:40<br>
<b><span style='font-weight:bold'>Til:</span></b>
Wien@zeus.theochem.tuwien.ac.at<br>
<b><span style='font-weight:bold'>Emne:</span></b> [Wien] How to set U in LDA+U
when computing the energy gap of HgTe</span></font><o:p></o:p></p>
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<p class=MsoNormal><font size=3 face=SimSun><span style='font-size:12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal style='margin-bottom:12.0pt'><font size=3 face=SimSun><span
style='font-size:12.0pt'>Dear users:<br>
</span></font><font face="Times New Roman"><span style='font-family:"Times New Roman"'> </span></font>
An article in PRB says: the energy gap of HgTe is -0.3<font
face="Times New Roman"><span style='font-family:"Times New Roman"'> </span></font>
.I use LDA+U to plot the energy band through adjusting U.But I didn't find the
overclapping of maximum valance band and the minimum conductivity band.They are
just combining.I think the energy gap is zero.But not -0.3.<font
face="Times New Roman"><span style='font-family:"Times New Roman"'> </span></font>
What could I do? The method of LDA+U is well for HgTe or HgSe?What'the value of
U?<br>
<font face="Times New Roman"><span style='font-family:"Times New Roman"'> </span></font>
Thank you for advance.<br>
<br>
<font face="Times New Roman"><span style='font-family:"Times New Roman"'> </span></font>
Mary<o:p></o:p></p>
<p><font size=3 face=SimSun><span style='font-size:12.0pt'> <o:p></o:p></span></font></p>
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<p class=MsoNormal><font size=3 face=SimSun><span style='font-size:12.0pt'><a
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