<div><DIV style="font-family:Georgia; color:#000000; font-size:13px;">Dear Juanjo,<BR><BR>As far as I know, metaGGAs are like GGAs for gaps: there are not accurate. For getting good gaps you have to switch to hybrid functionals or GW formalism (not implemented in QE though). Depending on what you want to do, of course, and if you know the gap value you may try this: optimize with a standard GGA functional, run a nscf calculation and if the gap is not totally closed up then operate a rigid band shifting for further properties calculations. This is a bit brute force...<BR><BR>If you do not know the gap value: run a hybrid single point calculation on the GGA optimized structure.<BR><BR>As Yves said, there are not so many options...<BR><BR>Pascal<BR><BR><BR><DIV style="WORD-WRAP: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space" dir="ltr">"Juanjo Meléndez" <melendez@unex.es> wrote:<BLOCKQUOTE type="cite" cite="<416A1BAAEB7E458788C55A933E8C9BCA@Otello>">
<DIV dir="ltr">
<DIV style="FONT-SIZE: 12pt; FONT-FAMILY: 'Calibri'; COLOR: #000000">
<DIV>Dear Yves</DIV>
<DIV> </DIV>
<DIV>Thanks a lot for your comments. Unfortunately, I need a good description of
gaps to calculate optical absorption, and hybrid functionals are prohibitive for
the supercells that I need to use. That is why I started to try with
metaGGA.</DIV>
<DIV> </DIV>
<DIV>I will have a look to the paper you mention (which I did not know, by the
way, thanks!) for more ideas...</DIV>
<DIV> </DIV>
<DIV>Take care</DIV>
<DIV> </DIV>
<DIV>Juanjo</DIV>
<DIV style="FONT-SIZE: small; FONT-FAMILY: 'Calibri'; FONT-WEIGHT: normal; COLOR: #000000; FONT-STYLE: normal; TEXT-DECORATION: none; DISPLAY: inline">
<DIV style="FONT: 10pt tahoma">
<DIV><FONT face="Calibri" size="3"></FONT> </DIV>
<DIV style="BACKGROUND: #f5f5f5">
<DIV style="font-color: black"><B>From:</B> <A title="yves.ferro@univ-amu.fr" href="mailto:yves.ferro@univ-amu.fr">Yves Ferro</A> </DIV>
<DIV><B>Sent:</B> Friday, October 31, 2014 10:20 AM</DIV>
<DIV><B>To:</B> <A title="pw_forum@pwscf.org" href="mailto:pw_forum@pwscf.org">PWSCF Forum</A> </DIV>
<DIV><B>Subject:</B> Re: [Pw_forum] TB09 metaGGA</DIV></DIV></DIV>
<DIV> </DIV></DIV>
<DIV style="FONT-SIZE: small; FONT-FAMILY: 'Calibri'; FONT-WEIGHT: normal; COLOR: #000000; FONT-STYLE: normal; TEXT-DECORATION: none; DISPLAY: inline">Dear
Juanjo,
<DIV> </DIV>
<DIV>From what I can remember:</DIV>
<DIV>- t<SPAN class="Apple-style-span" style="FONT-SIZE: 13px; FONT-FAMILY: georgia">he meta-GGA kinetic terms are not
saved in order to restart a nscf, at least up to the 5.0 version,</SPAN></DIV>
<DIV><FONT class="Apple-style-span" face="georgia"><SPAN class="Apple-style-span" style="FONT-SIZE: 13px">- the tools for building meta-GGA PPs are not available
in QE.</SPAN></FONT></DIV>
<DIV><FONT class="Apple-style-span" face="georgia"><SPAN class="Apple-style-span" style="FONT-SIZE: 13px">However, I'm not sure using meta-GGA pseudos will solve
your problem. Meta-GGA are known to have numerical instabilities such as the
ones you met, in particular when then electronic density drop to a very low
level as probably in your ionic crystal LiF, on the contrary with Si and C that
form covalent structures.</SPAN></FONT></DIV>
<DIV><FONT class="Apple-style-span" face="georgia"><SPAN class="Apple-style-span" style="FONT-SIZE: 13px"><BR></SPAN></FONT></DIV>
<DIV><FONT class="Apple-style-span" face="georgia"><SPAN class="Apple-style-span" style="FONT-SIZE: 13px">You can have a look to this paper you probably
know:</SPAN></FONT></DIV>
<DIV><FONT class="Apple-style-span" face="georgia"><SPAN class="Apple-style-span" style="FONT-SIZE: 13px">E.R. Johnson, JCP </SPAN></FONT><B>131</B>, 034111
2009</DIV>
<DIV><FONT class="Apple-style-span" face="georgia"><SPAN class="Apple-style-span" style="FONT-SIZE: 13px"><BR></SPAN></FONT></DIV>
<DIV><FONT class="Apple-style-span" face="georgia"><SPAN class="Apple-style-span" style="FONT-SIZE: 13px">I don't believe a cure to you problem exists at the
moment, except by changing the functional to a GGA one.</SPAN></FONT></DIV>
<DIV><FONT class="Apple-style-span" face="georgia"><SPAN class="Apple-style-span" style="FONT-SIZE: 13px"><BR></SPAN></FONT></DIV>
<DIV><SPAN class="Apple-style-span" style="FONT-SIZE: 13px; FONT-FAMILY: georgia">Best regards,</SPAN></DIV>
<DIV><FONT class="Apple-style-span" face="georgia"><SPAN class="Apple-style-span" style="FONT-SIZE: 13px"><BR></SPAN></FONT></DIV>
<DIV><FONT class="Apple-style-span" face="georgia"><SPAN class="Apple-style-span" style="FONT-SIZE: 13px">Yves</SPAN></FONT></DIV>
<DIV><FONT class="Apple-style-span" face="georgia"><SPAN class="Apple-style-span" style="FONT-SIZE: 13px">. </SPAN></FONT></DIV>
<DIV><FONT class="Apple-style-span" face="georgia"><SPAN class="Apple-style-span" style="FONT-SIZE: 13px"><BR></SPAN></FONT></DIV>
<DIV><FONT class="Apple-style-span" face="georgia"><SPAN class="Apple-style-span" style="FONT-SIZE: 13px"><BR></SPAN></FONT>
<DIV>
<DIV>Le 31 oct. 2014 à 09:26, Juanjo Meléndez a écrit :</DIV><BR class="Apple-interchange-newline">
<BLOCKQUOTE type="cite">
<DIV dir="ltr">
<DIV dir="ltr">
<DIV style="FONT-SIZE: 12pt; FONT-FAMILY: 'Calibri'; COLOR: #000000">
<DIV>Hi Pascal</DIV>
<DIV> </DIV>
<DIV>Thanks for replying. I agree with you that building a PP consistent with
the metaGGA functional would solve most of the instability problems. But I do
not have *any* experience building PPs (which, by the way, seems to be not
trivial to me, even less trivial for metaGGA), so I followed <A title="http://dx.doi.org/10.1016/j.cpc.2013.02.020" style="TEXT-ALIGN: justify" href="http://dx.doi.org/10.1016/j.cpc.2013.02.020">http://dx.doi.org/10.1016/j.cpc.2013.02.020</A>
and tried the trick. I was just wondering if any general strategy for
convergence exists. </DIV>
<DIV> </DIV>
<DIV>Regarding point 2, I asked one of the authors of the aforementioned paper
and he declared not the have seen such a problem before, so I guess that the
kinetic terms are not responsible. I have overcome the problem by using a
dense kpoints path already in scf calculations and calculating the bands
without the standard intermediate nscf run, but it would be nice if the
developers could have a look and check. </DIV>
<DIV> </DIV>
<DIV>Again, thank you very much for your interest.</DIV>
<DIV> </DIV>
<DIV>Juanjo</DIV>
<DIV> </DIV>
<DIV style="FONT-SIZE: 12pt; FONT-FAMILY: 'Calibri'; COLOR: #000000">Juan J.
Meléndez <BR>Associate Professor<BR>Department of Physics · University of
Extremadura<BR>Avda. de Elvas, s/n 06006 Badajoz (Spain)<BR>Phone: +34 924 28
96 55<BR>Fax: <A href="tel:+34924289651" target="_blank"><A href="tel:+34924289651" target="_blank">+34 924 28 96 51</A></A><BR>Email: <A href="mailto:melendez@unex.es">melendez@unex.es</A><BR>Web: <A href="http://materiales.unex.es/miembros/personal/jj-melendez/Index.html">http://materiales.unex.es/miembros/personal/jj-melendez/Index.html</A></DIV>
<DIV style="FONT-SIZE: small; FONT-FAMILY: 'Calibri'; FONT-WEIGHT: normal; COLOR: #000000; FONT-STYLE: normal; TEXT-DECORATION: none; DISPLAY: inline">
<DIV style="FONT: 10pt tahoma">
<DIV><FONT face="Calibri" size="3"></FONT> </DIV>
<DIV style="BACKGROUND: #f5f5f5">
<DIV style="font-color: black"><B>From:</B> <A title="pascal.boulet@univ-amu.fr" href="mailto:pascal.boulet@univ-amu.fr">Pascal BOULET</A> </DIV>
<DIV><B>Sent:</B> Thursday, October 30, 2014 7:15 PM</DIV>
<DIV><B>To:</B> <A title="pw_forum@pwscf.org" href="mailto:pw_forum@pwscf.org">PWSCF Forum</A> </DIV>
<DIV><B>Subject:</B> Re: [Pw_forum] TB09 metaGGA</DIV></DIV></DIV>
<DIV> </DIV></DIV>
<DIV style="FONT-SIZE: small; FONT-FAMILY: 'Calibri'; FONT-WEIGHT: normal; COLOR: #000000; FONT-STYLE: normal; TEXT-DECORATION: none; DISPLAY: inline">
<DIV>
<DIV style="FONT-SIZE: 13px; FONT-FAMILY: georgia; COLOR: #000000">hello,
<DIV> </DIV>
<DIV>I have never tried meta-GGA functionals with QE, so I am guessing. </DIV>
<DIV> </DIV>
<DIV>For point 1, one possible reason is the inadequacy between the pseudo
potential and the functional. I guess you have build a special pseudopotential
for this functional.</DIV>
<DIV> </DIV>
<DIV>Point 2: Could it be because the meta-GGA kinetic terms are not saved in
the checkpoint file and hence not readable when doing the
nscf?<BR><BR><BR>Pascal</DIV>
<DIV> </DIV>
<DIV>
<DIV> </DIV>
<DIV dir="ltr">"Juanjo Meléndez" <<A href="mailto:melendez@unex.es">melendez@unex.es</A>> wrote:
<BLOCKQUOTE cite="x-msg://4/%3CBA0A7E01AFE046D08178A05800725F9D@Otello%3E" type="cite">
<DIV dir="ltr">
<DIV style="FONT-SIZE: 12pt; FONT-FAMILY: 'Calibri'; COLOR: #000000">
<DIV>Hi all</DIV>
<DIV> </DIV>
<DIV align="justify">I am starting to work with metaGGA functionals in QE (v.
5.1 + libXc), following Èric Germaneau and colleagues’ work (<A title="http://dx.doi.org/10.1016/j.cpc.2013.02.020" href="http://dx.doi.org/10.1016/j.cpc.2013.02.020">http://dx.doi.org/10.1016/j.cpc.2013.02.020</A>).
I know that metaGGA is little tested, but I would be pleased if somebody
could answer a couple of questions:</DIV>
<DIV align="justify"> </DIV>
<DIV align="justify">1) Convergence is quite tricky. Up to know, I got some
results in simple systems using a very small mixing_beta (within 0.01–0.05),
not too many bands (just one or two conduction bands, never converged for
more bands) and restarting from a previously fully converged calculation. I
got results only for carbon, silicon and germanium, never got any
convergence for any binary simple compound (like LiF). Does anyone have
additional hints for metaGGA calculations to converge?</DIV>
<DIV align="justify"> </DIV>
<DIV align="justify">2) In addition, I get something wrong with nscf
calculations. After convergence of a scf run, I get a list of bands at each
k-point, as usual –nothing strange here. Then I made a path of k-points to
get the band structure and run a nscf calculation. This finishes fine as
well, but the bands are not only different from those from the scf
calculations, but also unrealistically high. I am attaching the input and
output files for both the scf and nscf runs, as well as a couple of
eigenval.xml files taken after nscf. Does anybody know how to manage this?
Or could this be a bug in the code?</DIV>
<DIV> </DIV>
<DIV>Thanks a lot in advance</DIV>
<DIV> </DIV>
<DIV>Take care</DIV>
<DIV> </DIV>
<DIV>Juanjo</DIV>
<DIV> </DIV>
<DIV style="FONT-SIZE: 12pt; FONT-FAMILY: 'Calibri'; COLOR: #000000">Juan J.
Meléndez <BR>Associate Professor<BR>Department of Physics · University of
Extremadura<BR>Avda. de Elvas, s/n 06006 Badajoz (Spain)<BR>Phone: +34 924
28 96 55<BR>Fax: <A href="tel:+34924289651" target="_blank">+34 924 28 96
51</A><BR>Email: <A href="mailto:melendez@unex.es">melendez@unex.es</A><BR>Web: <A href="http://materiales.unex.es/miembros/personal/jj-melendez/Index.html">http://materiales.unex.es/miembros/personal/jj-melendez/Index.html</A></DIV>
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