Dear Rencong,
I believe that the last step in vc-relax calculations is made in
slightly different Brillouin zone (calculated in relaxed variable cell
parameters), so the pressure calculated in the last step may be
different from whose obtained in the previous step (where Brillouin zone
of the original cell was used convergence criteria with desired pressure
is checked).
It also seems to me that your pressure is rather small. May be it has
sense to increase the pressure to at least 10 kbar.
Sincerely yours,
M. V. Kondrin
On 26.05.2021 05:48, 连云龙 wrote:
Dear Rencong,
I had similar experiences when I use QE pw.x to relax structures under pressure
and I want to follow this conversation.
My experience is that, the behaviour and result of relaxation depend largely on
the pesudopotential.
It is also helpful to investigate the energy and pressure during the relaxation.
In order for other experts to help you, could you please provide:
(1) the pseudopotentials used in the calculation
(2) the entire output file of pw.x, or at least the section contains the final
coordinates? (search "End of BFGS" in the output file)
(3) your name and affiliation (this is the rule of the mailing list)
Best,
Yunlong
--
Yunlong LIAN ORCID : https://orcid.org/0000-0002-9474-2181 CSNS, Dongguan
Neutron Science Center Dongguan, Guangdong, P. R. China 连云龙 中国散裂中子源 中子科学部
A1-629 (内线 303) 中国广东省东莞市
-----Original Messages-----
From:Amadeus <[email protected]>
Sent Time:2021-05-25 15:22:02 (Tuesday)
To: users <[email protected]>
Cc:
Subject: [QE-users] under pressure PbTaSe2 vc-relax calculation
Dear QE developer
I did the structural relaxation calculation for Pb at pressure of 3kbar， this
is relax.in
&CONTROL
prefix='PbTaSe2',
calculation='vc-relax', pseudo_dir='../../', outdir='./tmp',
verbosity='high',
tprnfor=.true., tstress=.true., forc_conv_thr=1.0d-4, nstep=100,
/
&SYSTEM
ibrav= 0, nat= 4, ntyp= 3,
occupations = 'smearing', smearing = 'gauss', degauss = 1.0d-2,
ecutwfc = 50, ecutrho = 500,
/
&ELECTRONS
conv_thr = 1.0d-8
mixing_beta = 0.7d0
/
&IONS
/
&CELL
cell_dynamics = "bfgs"
press = 2.70000e+00
press_conv_thr =0.1
/
ATOMIC_SPECIES
Ta 180.9479 Ta.UPF
Pb 207.2 Pb.UPF
Se 78.96 Se.UPF
CELL_PARAMETERS (angstrom)
3.4834700000 0.0000000000 0.0000000000
-1.7417350000 3.0167735133 0.0000000000
0.0000000000 0.0000000000 9.4755300000
ATOMIC_POSITIONS (crystal)
Pb 0.0000000000 0.0000000000 0.0000000000
Se 0.0000000000 0.0000000000 0.3246710000
Ta 0.3333330000 0.6666670000 0.5000000000
Se 0.0000000000 0.0000000000 0.6753290000
K_POINTS {automatic}
15 15 5 0 0 0
In relax.in, press=3.0kbar. But after pw.x is done, relax.out show that total
stress (Ry/bohr**3) (kbar) P=-0.83, and This is inconsistent with
press=3. this is part of relax.out
[rencong@mu01 phonon]$ grep 'Computing stress (Cartesian axis) and pressure' -A
15 relax.out
....
Computing stress (Cartesian axis) and pressure
total stress (Ry/bohr**3) (kbar) P=
2.93
0.00002030 -0.00000000 0.00000000 2.99 -0.00 0.00
-0.00000000 0.00002030 -0.00000000 -0.00 2.99 -0.00
-0.00000000 0.00000000 0.00001921 -0.00 0.00 2.83
kinetic stress (kbar) 26877.23 0.00 0.00
0.00 26877.23 -0.00
0.00 0.00 26796.57
local stress (kbar)-103340.53 0.03 0.00
0.03-103340.50 0.00
0.00 0.00 89394.48
nonloc. stress (kbar) 7797.15 0.00 0.00
--
Computing stress (Cartesian axis) and pressure
total stress (Ry/bohr**3) (kbar) P=
2.96
0.00002009 -0.00000000 0.00000000 2.96 -0.00 0.00
-0.00000000 0.00002009 -0.00000000 -0.00 2.96 -0.00
0.00000000 -0.00000000 0.00002028 0.00 -0.00 2.98
kinetic stress (kbar) 26879.49 0.00 0.00
0.00 26879.49 -0.00
0.00 -0.00 26798.86
local stress (kbar)-103299.75 0.03 0.00
0.03-103299.72 0.00
0.00 0.00 89348.84
nonloc. stress (kbar) 7797.79 -0.00 0.00
--
Computing stress (Cartesian axis) and pressure
total stress (Ry/bohr**3) (kbar) P=
-0.83
-0.00000653 -0.00000000 -0.00000000 -0.96 -0.00 -0.00
0.00000000 -0.00000653 0.00000000 0.00 -0.96 0.00
0.00000000 0.00000000 -0.00000384 0.00 0.00 -0.56
kinetic stress (kbar) 26883.07 0.00 -0.00
0.00 26883.07 -0.00
-0.00 -0.00 26802.38
local stress (kbar)-103303.36 0.03 0.00
0.03-103303.33 0.00
0.00 0.00 89345.22
nonloc. stress (kbar) 7795.83 -0.00 0.00
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_______________________________________________
Quantum ESPRESSO is supported by MaX (www.max-centre.eu)
users mailing list [email protected]
https://lists.quantum-espresso.org/mailman/listinfo/users
