<div dir="ltr">Hi, Xiaolin, I think you may want to support your colleagues' observations in Raman, actually you can use the phonon spectrum to explain what you have onserved given by phonon calculations in pwscf.<div>However, you must use more grid to produce quite accurate frequencies. Please also take care of the convergence of the grid to which some materials are very sensitive.</div><div><br></div><div>Bests</div><div>Fang</div><div class="gmail_extra"><br><div class="gmail_quote">2015-10-30 20:38 GMT+08:00 Jiqiang Li <span dir="ltr"><<a href="mailto:jqli14@fudan.edu.cn" target="_blank">jqli14@fudan.edu.cn</a>></span>:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div>
<div><span></span>Hi, Xiaolin,</div><div> Actually, you can use the gamma-only specific algorithm. N.B., you should use phcg.x instead of ph.x for the phonon calculation.</div><div><br></div><div>Jiqiang</div>
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<blockquote style="margin-top:0px;margin-bottom:0px;margin-left:0.5em"><div> </div><div style="border:none;border-top:solid #b5c4df 1.0pt;padding:3.0pt 0cm 0cm 0cm"><div style="PADDING-RIGHT:8px;PADDING-LEFT:8px;FONT-SIZE:12px;FONT-FAMILY:tahoma;COLOR:#000000;BACKGROUND:#efefef;PADDING-BOTTOM:8px;PADDING-TOP:8px"><div><b>From:</b> <a href="mailto:xiaolin0314@gmail.com" target="_blank">Xiaolin Xu</a></div><div><b>Date:</b> 2015-10-30 13:37</div><div><b>To:</b> <a href="mailto:Ari.P.Seitsonen@iki.fi" target="_blank">Ari Paavo Seitsonen</a>; <a href="mailto:pw_forum@pwscf.org" target="_blank">PWSCF Forum</a></div><div><b>Subject:</b> Re: [Pw_forum] phonon calculation not converge</div></div></div><div><div class="h5"><div><div><div dir="ltr">Dear Ari and Jiqiang,<div><br></div><div>Thank you so much for all the instructions! Yes I ran pw.x using <span style="font-size:13px">K_POINTS automatic // 1 1 1 0 0 0 before running ph.x. </span>I will increase the cut-off energy and hope it will work!</div><div><br></div><div>Lin</div></div><div class="gmail_extra"><br><div class="gmail_quote">On Thu, Oct 29, 2015 at 3:34 PM, Ari P Seitsonen <span dir="ltr"><<a href="mailto:Ari.P.Seitsonen@iki.fi" target="_blank">Ari.P.Seitsonen@iki.fi</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex"><br>
Dear Xiaolin, Jiqiang et co,<br>
<br>
Did you re-run 'pw.x' using the 'K_POINTS automatic // 1 1 1 0 0 0' before trying to run 'ph.x'?<br>
<br>
On the other hand the number of k points depends on your system, the amount of band dispersion it etc. So indeed, if the electronic structure is not yet converged well with only Gamma point, it is better to apply more k points. This you can do by testing for the convergence.<br>
<br>
By the way, the cut-off energy of 80 Ry is probably far too low for the HGH/GTH pseudo potentials that you have used: We used 125 Ry for the oxygen - I would guess that the one for iron, maybe also lithium - and that was in molecular dynamics; for phonons I would expect even higher a value necessary.<br>
<br>
Greetings,<br>
<br>
apsi<br>
<br>
-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-<br>
Ari Paavo Seitsonen / <a href="mailto:Ari.P.Seitsonen@iki.fi" target="_blank">Ari.P.Seitsonen@iki.fi</a> / <a href="http://www.iki.fi/~apsi/" rel="noreferrer" target="_blank">http://www.iki.fi/~apsi/</a><br>
Ecole Normale Supérieure (ENS), Département de Chimie, Paris<br>
Mobile (F) : <a href="tel:%2B33%20789%2037%2024%2025" value="+33789372425" target="_blank">+33 789 37 24 25</a> (CH) : <a href="tel:%2B41%2079%2071%2090%20935" value="+41797190935" target="_blank">+41 79 71 90 935</a><div><div><br>
<br>
<br>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex">
<br>
在 2015-10-30 00:26:09，"Xiaolin Xu" <<a href="mailto:xiaolin0314@gmail.com" target="_blank">xiaolin0314@gmail.com</a>> 写道：<br>
<br>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex">
Hi Jiqiang,<br>
<br>
<br>
Thank you very much for your help! <br>
I tried using only gamma point, but I got an error message when I calculated phonon saying "can't start from gamma tricks...". Besides, I need to calculate the raman frequencies after phonon calculation, so I think it's better if I use more k points.<br>
<br>
Have you tried Raman calculation? Could you give me more advice?<br>
<br>
Best,<br>
<br>
Xiaolin<br>
<br>
<br>
On Wed, Oct 28, 2015 at 10:21 PM, Xiaolin Xu <<a href="mailto:xxu2@caltech.edu" target="_blank">xxu2@caltech.edu</a>> wrote:<br>
<br>
Hi Jiqiang,<br>
<br>
Thank you very much for your help! <br>
I tried using only gamma point, but I got an error message when I calculated phonon saying "can't start from gamma tricks...". Besides, I need to calculate the raman frequencies after phonon calculation, so I think it's better if I use more k points.<br>
<br>
Have you tried Raman calculation? Could you give me more advice?<br>
<br>
Best,<br>
<br>
Xiaolin<br>
<br>
<br>
On Wed, Oct 28, 2015 at 6:20 PM, jqli14 <<a href="mailto:jqli14@fudan.edu.cn" target="_blank">jqli14@fudan.edu.cn</a>> wrote:<br>
(1)employ k_points gamma instead of k_pionts automatic 1 1 1 0 0 0, although both give the same result, but the later does not call the gamma point specific algorithm to speed the calculation.<br>
(2)if it can not converge within handreds of electronic steps, reduce the value of mixing_beta or change the mixing_mode.<br>
<br>
Jiqiang Li<br>
<br>
<br>
在 2015-10-29 07:57:58，"Xiaolin Xu" <<a href="mailto:xiaolin0314@gmail.com" target="_blank">xiaolin0314@gmail.com</a>> 写道：<br>
<br>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex">
Dear all,<br>
<br>
I was doing phonon dispersion calculations for lithium iron phosphate. However, the calculation speed is really slow and it does not converge. Is this because my system is too big? There are 28 atoms in the unit cell. My input file is like this:<br>
(1)<br>
<br>
<br>
&CONTROL<br>
calculation = "scf",<br>
pseudo_dir = "/home/xiaolin/pseudo",<br>
outdir = "/home/xiaolin/test2",<br>
tstress=.true.,<br>
tprnfor=.true.,<br>
nstep=100,<br>
/<br>
<br>
&SYSTEM<br>
ibrav = 8,<br>
celldm(1) = 19.749526<br>
celldm(2) = 0.582432,<br>
celldm(3) = 0.454693,<br>
nat = 28,<br>
ntyp = 4,<br>
ecutwfc = 80.D0,<br>
/<br>
<br>
&ELECTRONS<br>
mixing_beta = 0.7,<br>
/<br>
<br>
&IONS<br>
/<br>
<br>
ATOMIC_SPECIES<br>
<br>
Li 6.941 Li.pbe-s-hgh.UPF<br>
Fe 55.845 Fe.pbe-sp-hgh.UPF<br>
P 30.97376 P.pbe-hgh.UPF<br>
O 15.9994 O.pbe-hgh.UPF<br>
ATOMIC_POSITIONS (alat)<br>
Li 0 0 0<br>
...<br>
K_POINTS (automatic)<br>
1 1 1 0 0 0<br>
<br>
(2)<br>
<br>
Normal modes for lifepo4<br>
&inputph<br>
tr2_ph=1.5d-5,<br>
amass(1)=6.941,<br>
amass(2)=55.845,<br>
amass(3)=30.97376,<br>
amass(4)=15.9994,<br>
outdir = '/home/xiaolin/test2',<br>
trans=.true.,<br>
asr=.true.,<br>
nogg=.true.,<br>
fildyn='dmat.lifepo4'<br>
/<br>
0.0 0.0 0.0<br>
<br>
<br>
<br>
Thank you in advance!<br>
<br>
<br>
Lin<br>
</blockquote>
<br>
<br>
<br>
</blockquote>
</blockquote>
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