Hello, Xavier! Is all these efforts (increasing ecut to 200 Ry) are just
make one to believe that frequency of acoustic modes at Gamma point is
zero?
Sincerely yours,
M. V. Kondrin
On Oct 27 2022, Bidault, Xavier wrote:
Hello Ramesh,
Norm-conserving (NC) pseudopotentials (PP) require higher energy cutoffs.
You need NC PP for electron-phonon calculations. NC PP from PseudoDojo
website are very good, at least for what I've tested on organic
materials. Then you don't need ecutrho for NC PP, which are made to work
with default ecutrho = 4 x ecutwfc.
So, you should try first to increase your cutoff, up to 200 Ry should do
the job to have the asymptotic behavior with PseudoDojo NC PP
(unfortunately, other NC PP may require much higher cutoffs to get the
asymptotic behavior). Then you can choose the cutoff where the asymptotic
error is just below 1 meV/atom.
After you do a vc-relax simulation, always check the verification step at
the end of the output. If the pressure tensor is different from the
pressure tensor of the last optimization step, then it means your cutoff
is not large enough, or your system has converging issues (initial
geometry, k-points...).
I think your forc_conv_thr of 1e-4 is good. You can tighten a little bit
etot_conv_thr to 1e-5 and press_conv_thr to 0.1 kbar.
Regards, Xavier ________________________________ From: users
<users-boun...@lists.quantum-espresso.org> on behalf of Ramesh Kumar
Kamadurai via users <users@lists.quantum-espresso.org> Sent: Thursday,
October 27, 2022 3:23 AM To: users@lists.quantum-espresso.org
<users@lists.quantum-espresso.org> Subject: [QE-users] Electron Phonon
Calculation: tolerance limit for P
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
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