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<title>Re: [Wien] Suggestions on PHONON Calculation 4</title>
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<p class=MsoNormal><font size=2 face="Times New Roman"><span style='font-size:
11.0pt'>Dear Dr.Blaha, <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face="Times New Roman"><span style='font-size:
11.0pt'>Thank you <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face="Times New Roman"><span style='font-size:
11.0pt'>That is exactly what I got when I plotted the force constants (far
distance f.c. are still not converged)<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face="Times New Roman"><span style='font-size:
11.0pt'>Thanks for the hint. <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face="Times New Roman"><span style='font-size:
11.0pt'>I have now taken an 18 atom as well as 24 atom supercell. <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face="Times New Roman"><span style='font-size:
11.0pt'>Let us see what happens <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face="Times New Roman"><span style='font-size:
11.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face="Times New Roman"><span style='font-size:
11.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face="Times New Roman"><span style='font-size:
11.0pt'><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'>From:</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'>On Behalf Of </span></b><st2:PersonName w:st="on"><st1:GivenName w:st="on">Peter</st1:GivenName>
<st1:Sn w:st="on">Blaha</st1:Sn></st2:PersonName><br>
<b><span style='font-weight:bold'>Sent:</span></b> Thursday, February 10, 2011
6:30 PM<br>
<b><span style='font-weight:bold'>To:</span></b> <st2:PersonName w:st="on"><st1:GivenName
w:st="on">A</st1:GivenName> <st1:middlename w:st="on">Mailing list</st1:middlename>
<st1:middlename w:st="on">for</st1:middlename> <st1:middlename w:st="on">WIEN2k</st1:middlename>
<st1:Sn w:st="on">users</st1:Sn></st2:PersonName><br>
<b><span style='font-weight:bold'>Subject:</span></b> Re: [<st1:Sn w:st="on">Wien</st1:Sn>]
Suggestions on PHONON Calculation 4</span></font><o:p></o:p></p>
</div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p><font size=2 face="Times New Roman"><span style='font-size:10.0pt'>If your
supercell contains only 12 atoms ?? it is a very small supercell.<br>
<br>
Thus only on very few q-points the phonons will be correct, while using such a
small<br>
cell the phonons on other q-points can be completely wrong.<br>
<br>
When you plot the force constants, you should see that the far distance f.c.
are still not<br>
converged (small).<br>
<br>
No, I don't want you dsy file.<br>
<br>
When the "sum of forces" during analyse_phonon are small for every
displacement, there<br>
is no problem with the WIEN2k calculations.<br>
<br>
Please read the phonon manual. It is clearly said there, that you need a
sizable supercell!<br>
<br>
Am 10.02.2011 13:13, schrieb <st2:PersonName w:st="on"><st1:GivenName w:st="on">Ghosh</st1:GivenName>
<st1:Sn w:st="on">SUDDHASATTWA</st1:Sn></st2:PersonName>:<br>
> Dear Dr.Blaha,<br>
><br>
> I am sorry I have posted this question before.<br>
><br>
> I guess my querie may be inappropriate in the Wien2k mailing list. Still,
first I would request <st2:PersonName w:st="on"><st1:title w:st="on">Prof.</st1:title>
<st1:Sn w:st="on">Blaha</st1:Sn></st2:PersonName> to kindly give me permission
and help me in sorting the issue in PHONON<br>
> which actually is not a Wien2k problem.<br>
><br>
> After I imported the case.dsy file ( forces convergence obtained with
0.005 mRy) in phonon software and incorporated the lattice parameters of the
supercell and the number of<br>
> atoms, I applied the translational and rotational invariances, I get the
Do Report in PHONON.<br>
><br>
> I get the plot of force constants and I subsequently get the phonon
dispersion. I get some imaginary frequencies which I am not sure if it is because
of the wrong choice of<br>
> supercell size (12 atoms) or the force convergence (0.005 mRy/atom)<br>
><br>
> Can you please help me in this regard?<br>
><br>
> Can I send you the case.dsy for your perusal?<br>
><br>
> Thank you<br>
><br>
> Suddhasattwa<br>
><br>
><br>
><br>
> _______________________________________________<br>
> <st1:Sn w:st="on">Wien</st1:Sn> mailing list<br>
> Wien@zeus.theochem.tuwien.ac.at<br>
> <a href="http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien">http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien</a><br>
<br>
--<br>
<br>
P.Blaha<br>
--------------------------------------------------------------------------<br>
<st2:PersonName w:st="on"><st1:GivenName w:st="on">Peter</st1:GivenName> <st1:Sn
w:st="on">BLAHA</st1:Sn></st2:PersonName>, Inst.f. Materials Chemistry, TU
Vienna, A-1060 <st2:City w:st="on"><st2:place w:st="on">Vienna</st2:place></st2:City><br>
Phone:
+43-1-58801-15671
FAX: +43-1-58801-15698<br>
Email: blaha@theochem.tuwien.ac.at WWW: <a
href="http://info.tuwien.ac.at/theochem/">http://info.tuwien.ac.at/theochem/</a><br>
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