Dear all,
I'm currently running an NPT molecular dynamics simulation of the MgSiO3
system (80 atoms) under ambient conditions (0 GPa, 300 K) on qe-7.4.1, and
I was hoping to get your advice on an issue I'm facing with pressure
control.
Even though I’ve set the target pressure to 0 GPa for 2000 steps, the
time-averaged pressure over several thousand steps stays about 0.5 GPa
lower than expected. I also checked using a moving average, the pressure
doesn’t reach the target.
So far, I’ve tried several approaches to reduce Pulay stress and improve
pressure convergence:
Increased the plane-wave cutoff energy to 80 Ry
Tested different values of the `nraise` parameter
Doubled the system size from 80 to 160 atoms to reduce finite-size effects
Switched the cell dynamics from `pr` (Parrinello-Rahman) to `w`
(Wentzcovitch)
Unfortunately, neither change made much of a difference.
If anyone has encountered similar issues or has suggestions on how to
improve pressure convergence and achieve better equilibration, I would
greatly appreciate your input.
Seitaro Yazawa
graduate student
Department of Earth and Planetary science
Univ. Tokyo
&control
calculation = 'vc-md'
prefix='bridgmanite',
tstress = .true.
tprnfor = .true.
pseudo_dir = './pseudopotential',
outdir='./work/'
nstep = 2000
disk_io = 'low'
/
&system
ibrav = 0,
nat = 80,
ntyp = 3,
ecutwfc = 50.0,
ecutrho = 300.0,
occupations = 'smearing'
smearing = 'm-p'
degauss = 0.01
nosym=.true.
/
&electrons
mixing_beta = 0.7
conv_thr = 1.0d-5
/
&ions
ion_temperature = 'rescaling'
tempw = 300
nraise = 100
tolp = 10
/
&cell
cell_dynamics = 'pr'
press = 0
cell_dofree = 'xyz'
/
ATOMIC_SPECIES
Mg 24.3050 Mg.pbe-n-kjpaw_psl.0.3.0.UPF
Si 28.0855 Si.pbe-n-kjpaw_psl.0.1.UPF
O 15.9994 O.pbe-n-kjpaw_psl.0.1.UPF
ATOMIC_POSITIONS {angstrom}
Mg 2.4406190140 2.8727780929 1.7912494919
Mg 2.2985751016 2.3133781666 5.2791667246
Mg 0.0273236948 4.8015879094 5.2790920900
Mg 4.7118622874 0.3845670807 1.7913274731
Si 2.3696574944 0.1048379856 3.5349811056
Si -0.0431827922 2.5930428386 3.5348865041
Si 2.3701118078 0.1051587079 0.0469825522
Si -0.0427270638 2.5933628517 0.0468866746
O 0.4574649955 2.4187818519 1.7909459951
O 4.2817269017 2.7673678905 5.2794534229
O 2.8698492588 0.2790656557 5.2790494327
O 1.8693379325 4.9070854303 1.7913489149
O 0.9046391591 1.1080890629 3.9091481999
O 3.8345380314 4.0780493924 3.1612443211
O 3.3175234703 1.5897700456 3.1609566527
O 1.4216780631 3.5963710921 3.9094349151
O 3.8349023079 4.0783140121 0.4217844016
O 0.9042897177 1.1078570373 6.6486135341
O 1.4213168198 3.5961372909 6.6489013495
O 3.3178763085 1.5900331398 0.4214993183
Mg 2.4404920313 7.8493131424 1.7916867735
Mg 2.2984477893 7.2899133197 5.2796049409
Mg 0.0271958832 9.7781221425 5.2795281801
Mg 4.7117344667 5.3611022758 1.7917673172
Si 2.3695299095 5.0813727127 3.5354195251
Si -0.0433095179 7.5695777251 3.5353244359
Si 2.3699848128 5.0816933874 0.0474207408
Si -0.0428544923 7.5698980568 0.0473247647
O 0.4573382344 7.3953169875 1.7913838757
O 4.2815997612 7.7439030226 5.2798903481
O 2.8697220975 5.2556005826 5.2794877501
O 1.8692103937 9.8836201825 1.7917861676
O 0.9045124121 6.0846242720 3.9095867606
O 3.8344100864 9.0545842859 3.1616804575
O 3.3173964094 6.5663045400 3.1613943153
O 1.4215507207 8.5729058161 3.9098727744
O 3.8347744935 9.0548490078 0.4222203388
O 0.9041623873 6.0843919705 6.6490520691
O 1.4211889342 8.5726721918 6.6493389621
O 3.3177490881 6.5665680889 0.4219365496
Mg 7.2661922862 2.8729005183 1.7918781973
Mg 7.1241479156 2.3135000475 5.2797966105
Mg 4.8528971111 4.8017100807 5.2797191998
Mg 9.5374341106 0.3846897857 1.7919582511
Si 7.1952301259 0.1049601528 3.5356107047
Si 4.7823907743 2.5931650797 3.5355159865
Si 7.1956849345 0.1052803854 0.0476120992
Si 4.7828458328 2.5934859144 0.0475165040
O 5.2830388066 2.4189039164 1.7915756351
O 9.1072998173 2.7674905575 5.2800817677
O 7.6954218063 0.2791874890 5.2796787609
O 6.6949111801 4.9072082874 1.7919778694
O 5.7302124789 1.1082117321 3.9097781551
O 8.6601103499 4.0781718542 3.1618721902
O 8.1430960609 1.5898920689 3.1615854057
O 6.2472512603 3.5964934522 3.9100645206
O 8.6604748686 4.0784362283 0.4224119483
O 5.7298621237 1.1079791843 6.6492438340
O 6.2468898094 3.5962594572 6.6495309669
O 8.1434495420 1.5901546743 0.4221277399
Mg 7.2660647945 7.8494350617 1.7923164356
Mg 7.1240210483 7.2900354819 5.2802335548
Mg 4.8527690433 9.7782448177 5.2801590548
Mg 9.5373069524 5.3612249442 1.7923954629
Si 7.1951031891 5.0814951781 3.5360483545
Si 4.7822633044 7.5697007251 3.5359533136
Si 7.1955573199 5.0818158845 0.0480495453
Si 4.7827185818 7.5700205114 0.0479535633
O 5.2829109209 7.3954396459 1.7920125894
O 9.1071726756 7.7440252329 5.2805201016
O 7.6952949011 5.2557231584 5.2801163477
O 6.6947836454 9.8837420320 1.7924157976
O 5.7300855066 6.0847470591 3.9102149976
O 8.6599830605 9.0547066212 3.1623110983
O 8.1429695926 6.5664270556 3.1620236108
O 6.2471235521 8.5730278400 3.9105014290
O 8.6603472223 9.0549702547 0.4228505347
O 5.7297355413 6.0845146085 6.6496800132
O 6.2467619709 8.5727943058 6.6499680905
O 8.1463435811 6.5676263992 0.4211232920
CELL_PARAMETERS {angstrom}
9.651145881 0.0 0.0
0.0 9.953069617 0.0
0.0 0.0 6.976003984
K_POINTS {automatic}
2 2 4 0 0 0
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