Hi, Xiaolin,
Actually, you can use the gamma-only specific algorithm. N.B., you
should use phcg.x instead of ph.x for the phonon calculation.
Jiqiang
From: Xiaolin Xu
Date: 2015-10-30 13:37
To: Ari Paavo Seitsonen; PWSCF Forum
Subject: Re: [Pw_forum] phonon calculation not converge
Dear Ari and Jiqiang,
Thank you so much for all the instructions! Yes I ran pw.x using K_POINTS
automatic // 1 1 1 0 0 0 before running ph.x. I will increase the cut-off
energy and hope it will work!
Lin
On Thu, Oct 29, 2015 at 3:34 PM, Ari P Seitsonen <[email protected]> wrote:
Dear Xiaolin, Jiqiang et co,
Did you re-run 'pw.x' using the 'K_POINTS automatic // 1 1 1 0 0 0' before
trying to run 'ph.x'?
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.
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.
Greetings,
apsi
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Ari Paavo Seitsonen / [email protected] / http://www.iki.fi/~apsi/
Ecole Normale Supérieure (ENS), Département de Chimie, Paris
Mobile (F) : +33 789 37 24 25 (CH) : +41 79 71 90 935
在 2015-10-30 00:26:09，"Xiaolin Xu" <[email protected]> 写道：
Hi Jiqiang,
Thank you very much for your help!
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.
Have you tried Raman calculation? Could you give me more advice?
Best,
Xiaolin
On Wed, Oct 28, 2015 at 10:21 PM, Xiaolin Xu <[email protected]> wrote:
Hi Jiqiang,
Thank you very much for your help!
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.
Have you tried Raman calculation? Could you give me more advice?
Best,
Xiaolin
On Wed, Oct 28, 2015 at 6:20 PM, jqli14 <[email protected]> wrote:
(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.
(2)if it can not converge within handreds of electronic steps, reduce the value
of mixing_beta or change the mixing_mode.
Jiqiang Li
在 2015-10-29 07:57:58，"Xiaolin Xu" <[email protected]> 写道：
Dear all,
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:
(1)
&CONTROL
calculation = "scf",
pseudo_dir = "/home/xiaolin/pseudo",
outdir = "/home/xiaolin/test2",
tstress=.true.,
tprnfor=.true.,
nstep=100,
/
&SYSTEM
ibrav = 8,
celldm(1) = 19.749526
celldm(2) = 0.582432,
celldm(3) = 0.454693,
nat = 28,
ntyp = 4,
ecutwfc = 80.D0,
/
&ELECTRONS
mixing_beta = 0.7,
/
&IONS
/
ATOMIC_SPECIES
Li 6.941 Li.pbe-s-hgh.UPF
Fe 55.845 Fe.pbe-sp-hgh.UPF
P 30.97376 P.pbe-hgh.UPF
O 15.9994 O.pbe-hgh.UPF
ATOMIC_POSITIONS (alat)
Li 0 0 0
...
K_POINTS (automatic)
1 1 1 0 0 0
(2)
Normal modes for lifepo4
&inputph
tr2_ph=1.5d-5,
amass(1)=6.941,
amass(2)=55.845,
amass(3)=30.97376,
amass(4)=15.9994,
outdir = '/home/xiaolin/test2',
trans=.true.,
asr=.true.,
nogg=.true.,
fildyn='dmat.lifepo4'
/
0.0 0.0 0.0
Thank you in advance!
Lin
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