<html>
<head>
<meta content="text/html; charset=windows-1252"
http-equiv="Content-Type">
</head>
<body bgcolor="#FFFFFF" text="#000000">
<div class="moz-cite-prefix">Dear Ramesh,<br>
<br>
It seems to me that some small negative values in phonon
calculations is unavoidable. They occur rather sporadically
(especially for acoustic modes in Gamma point) and the best way to
deal with them is just ignore them. For electron-phonon
calculations it is better not to use lambda.x program (it does not
tolerate negative frequencies) but follow the way described in
this thread --
<a class="moz-txt-link-freetext" href="https://lists.quantum-espresso.org/pipermail/users/2022-September/049463.html">https://lists.quantum-espresso.org/pipermail/users/2022-September/049463.html</a><br>
<br>
Sincerely yours,<br>
M.V. Kondrin<br>
<br>
On 10/27/2022 11:23 AM, Ramesh Kumar Kamadurai via users wrote:<br>
</div>
<blockquote
cite="mid:CAEtACp+v8W6CBnm-2rBmu2H2aSAOmEVjFAN32cDVCb9Es1V8_Q@mail.gmail.com"
type="cite">
<pre wrap="">Dear users
I am trying to calculate el-Ph coupling constant and other properties for a
superconductor. The input file is attached. I am a bit stuck with VC-Relax
calculation as the system is not able to stabilize at 0.0 kbar. I followed
all the suggestions given in forum
1. Increased Cut-off to maximum
2. Tried USPP,NC, Mixed and currently running with PBE-Sol
3. Sequentially done 2 VC Relax calculation but i am not able to sort out
the issue.
&CONTROL
calculation = "vc-relax"
etot_conv_thr = 4.00000e-05
forc_conv_thr = 1.00000e-04
max_seconds = 1.72800e+05
nstep = 100
outdir = "/home/sjacobs/tmp/"
prefix = "PDZ-VCRELAX"
pseudo_dir = "C:\Users\RAMESH\.burai\.pseudopot"
tprnfor = .TRUE.
tstress = .TRUE.
verbosity = "high"
/
&SYSTEM
a = 6.36512e+00
degauss = 7.34986e-03
ecutrho = 6.40000e+02
ecutwfc = 8.00000e+01
ibrav = 2
nat = 4
nosym = .FALSE.
nspin = 1
ntyp = 3
occupations = "smearing"
smearing = "marzari-vanderbilt"
/
&ELECTRONS
conv_thr = 8.00000e-10
electron_maxstep = 80
mixing_beta = 4.00000e-01
startingpot = "atomic"
startingwfc = "atomic+random"
/
&IONS
ion_dynamics = "bfgs"
/
&CELL
cell_dofree = "all"
cell_dynamics = "bfgs"
press = 0.00000e+00
press_conv_thr = 5.00000e-01
/
K_POINTS {automatic}
12 12 12 0 0 0
ATOMIC_SPECIES
Ga 69.72300 Ga.pbesol-dnl-rrkjus_psl.1.0.0.UPF
Pd 106.42000 Pd_ONCV_PBEsol-1.0.upf
Zr 91.22400 zr_pbesol_v1.uspp.F.UPF
ATOMIC_POSITIONS {crystal}
Zr 0.000000 0.000000 0.000000
Ga 0.493162 0.493162 0.493162
Pd 0.739743 0.739743 0.739743
Pd 0.246581 0.246581 0.246581
The output stress is given below
entering subroutine stress ...
total stress (Ry/bohr**3) (kbar) P=
2.67
entering subroutine stress ...
total stress (Ry/bohr**3) (kbar) P=
-0.41
entering subroutine stress ...
total stress (Ry/bohr**3) (kbar) P=
-0.82
entering subroutine stress ...
total stress (Ry/bohr**3) (kbar) P=
0.56
entering subroutine stress ...
total stress (Ry/bohr**3) (kbar) P=
0.13
entering subroutine stress ...
total stress (Ry/bohr**3) (kbar) P=
-0.08
entering subroutine stress ...
total stress (Ry/bohr**3) (kbar) P=
-0.23
entering subroutine stress ...
total stress (Ry/bohr**3) (kbar) P=
-0.35
entering subroutine stress ...
total stress (Ry/bohr**3) (kbar) P=
-0.50
entering subroutine stress ...
total stress (Ry/bohr**3) (kbar) P=
-0.63
entering subroutine stress ...
total stress (Ry/bohr**3) (kbar) P=
-0.77
entering subroutine stress ...
total stress (Ry/bohr**3) (kbar) P=
-0.83
My question is
What is the optimal pressure value to avoid negative frequencies for
electron phonon calculation ?
Is there any mistake in my input file ?
Thanks in advance
Regards
Ramesh
Asst. Professor
GITAM University
Vizag, India
</pre>
<br>
<fieldset class="mimeAttachmentHeader"></fieldset>
<br>
<pre wrap="">_______________________________________________
The Quantum ESPRESSO community stands by the Ukrainian
people and expresses its concerns about the devastating
effects that the Russian military offensive has on their
country and on the free and peaceful scientific, cultural,
and economic cooperation amongst peoples
_______________________________________________
Quantum ESPRESSO is supported by MaX (<a class="moz-txt-link-abbreviated" href="http://www.max-centre.eu">www.max-centre.eu</a>)
users mailing list <a class="moz-txt-link-abbreviated" href="mailto:users@lists.quantum-espresso.org">users@lists.quantum-espresso.org</a>
<a class="moz-txt-link-freetext" href="https://lists.quantum-espresso.org/mailman/listinfo/users">https://lists.quantum-espresso.org/mailman/listinfo/users</a></pre>
</blockquote>
<p><br>
</p>
</body>
</html>