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 <760158...@qq.com>
Sent Time:2021-05-25 15:22:02 (Tuesday)
To: users <users@lists.quantum-espresso.org>
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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