[Pw_forum] vc-relax : total force does not converge
Jiseok Kim
tube77 at gmail.com
Wed Sep 5 01:04:39 CEST 2012
Dear QE users,
I'm having a difficulty on a geometry optimization using 'vc-relax'.
I searched forum threads and followed various suggestions but the 'Total
force' still does not converge..
(but the pressures seems to be converged)
The job steps I've taken as follows,
1. optimized k-point and ecutwfc.
2. optimized lattice parameter using Murnaghan fitting.
3. 'relax' the geometry using the lattice constant obtained from step2,
----------------------------------------------
&control
calculation = 'relax',
restart_mode = 'from_scratch',
prefix = '$NAME',
pseudo_dir = '$PSEUDO_DIR/',
outdir = '$OUT_DIR/',
wf_collect = .TRUE.
tstress = .TRUE.
tprnfor = .TRUE.
etot_conv_thr = 1.d-7
forc_conv_thr = 1.d-6
nstep = 1000
/
&system
ibrav = 0,
celldm(1) = 10.3345
nat = 18,
ntyp = 2,
ecutwfc = 80.0,
/
&electrons
diagonalization = 'cg',
mixing_mode = 'plain',
mixing_beta = 0.7,
conv_thr = 1.0d-10,
/
&ions
ion_dynamics = 'bfgs'
bfgs_ndim = 3
/
ATOMIC_SPECIES
Si 28.086 Si.pbe-rrkj.UPF
H 1.0079 H.pbe-vbc.UPF
CELL_PARAMETERS
4.89897948556636 0.00000000000000 0.00000000000000
0.00000000000000 5.19615242270663 0.00000000000000
0.00000000000000 0.00000000000000 0.70710678118655
ATOMIC_POSITIONS angstrom
Si 6.65158939652772 10.19066526389879 0.00000000000000
Si 7.76018762928234 9.40676793590657 1.92014846431207
Si 9.97738409479158 10.19066526389879 1.92014846431207
Si 11.08598232754620 9.40676793590657 0.00000000000000
Si 13.30317879305544 10.19066526389879 0.00000000000000
Si 14.41177702581006 9.40676793590657 1.92014846431207
Si 16.62897349131930 10.19066526389879 1.92014846431207
Si 17.73757172407392 9.40676793590657 0.00000000000000
H 6.65158939652772 11.67767298594874 0.00000000000000
H 7.76018762928234 7.91976021385662 1.92014846431207
H 9.97738409479158 11.67767298594874 1.92014846431207
H 11.08598232754620 7.91976021385662 0.00000000000000
H 13.30317879305544 11.67767298594874 0.00000000000000
H 14.41177702581006 7.91976021385662 1.92014846431207
H 16.62897349131930 11.67767298594874 1.92014846431207
H 17.73757172407392 7.91976021385662 0.00000000000000
H 5.24962507127668 9.69499602321547 0.00000000000000
H 19.13953604932496 9.90243717658989 0.00000000000000
K_POINTS automatic
1 1 16 0 0 0
----------------------------------------------
4. check if 'Total force' is converged -> OK.
5. Take the final atomic coordinates from step4.
6. Run 'vc-relax' as,
----------------------------------------------
&control
calculation = 'vc-relax',
restart_mode = 'from_scratch',
prefix = '$NAME',
pseudo_dir = '$PSEUDO_DIR/',
outdir = '$OUT_DIR/',
wf_collect = .TRUE.
tstress = .TRUE.
tprnfor = .TRUE.
etot_conv_thr = 1.d-6
forc_conv_thr = 1.d-6
nstep = 10000
/
&system
ibrav = 0,
celldm(1) = 10.3345
nat = 18,
ntyp = 2,
ecutwfc = 80.0,
ecfixed = 70.0,
qcutz = 150.0,
q2sigma = 4.0,
/
&electrons
diagonalization = 'cg',
mixing_mode = 'plain',
mixing_beta = 0.7,
conv_thr = 1.0d-10,
/
&ions
ion_dynamics = 'bfgs'
bfgs_ndim = 3
/
&cell
cell_dynamics = 'bfgs'
press_conv_thr = 0.1d0
press = 0.d0
cell_factor = 2.d0
/
ATOMIC_SPECIES
Si 28.086 Si.pbe-rrkj.UPF
H 1.0079 H.pbe-vbc.UPF
CELL_PARAMETERS
4.89897948556636 0.00000000000000 0.00000000000000
0.00000000000000 5.19615242270663 0.00000000000000
0.00000000000000 0.00000000000000 0.70710678118655
ATOMIC_POSITIONS angstrom
Si 6.595371055 10.174313717 -0.005918138
Si 7.697686348 9.425353751 1.927575025
Si 9.940638827 10.152944754 1.927571298
Si 11.073523827 9.431959516 -0.005942277
Si 13.315586210 10.165270258 -0.005944217
Si 14.448496999 9.444343582 1.927568680
Si 16.691414457 10.172072841 1.927571881
Si 17.793848036 9.423269303 -0.005921592
H 6.597479872 11.672720999 -0.006012302
H 7.704912055 7.923796337 1.927472273
H 9.942740551 11.655007902 1.927566837
H 11.078852672 7.930134628 -0.005961188
H 13.310208995 11.667097994 -0.005963695
H 14.446478909 7.942288221 1.927563469
H 16.684085788 11.673634035 1.927468080
H 17.791980426 7.924865718 -0.006016781
H 5.166205416 9.718188689 -0.005743345
H 19.222939638 9.879636554 -0.005746296
K_POINTS automatic
1 1 16 0 0 0
----------------------------------------------
Then the output 'Total force' seems to oscillates and does not converge as
shown below,
----------------------------------------------------------------------------
-------------
Total force = 0.000723 Total SCF correction = 0.000009
Total force = 0.000288 Total SCF correction = 0.000010
Total force = 0.000172 Total SCF correction = 0.000001
Total force = 0.000227 Total SCF correction = 0.000005
Total force = 0.000323 Total SCF correction = 0.000005
Total force = 0.000327 Total SCF correction = 0.000004
Total force = 0.000393 Total SCF correction = 0.000004
Total force = 0.000682 Total SCF correction = 0.000004
Total force = 0.000811 Total SCF correction = 0.000006
Total force = 0.000803 Total SCF correction = 0.000007
Total force = 0.000427 Total SCF correction = 0.000001
Total force = 0.000392 Total SCF correction = 0.000002
Total force = 0.000380 Total SCF correction = 0.000001
Total force = 0.000233 Total SCF correction = 0.000001
Total force = 0.000164 Total SCF correction = 0.000001
Total force = 0.000227 Total SCF correction = 0.000001
Total force = 0.000246 Total SCF correction = 0.000000
Total force = 0.000299 Total SCF correction = 0.000001
Total force = 0.000320 Total SCF correction = 0.000001
Total force = 0.000230 Total SCF correction = 0.000001
Total force = 0.000129 Total SCF correction = 0.000001
Total force = 0.000147 Total SCF correction = 0.000000
Total force = 0.000131 Total SCF correction = 0.000001
Total force = 0.000104 Total SCF correction = 0.000000
Total force = 0.000116 Total SCF correction = 0.000001
Total force = 0.000146 Total SCF correction = 0.000000
Total force = 0.000180 Total SCF correction = 0.000001
Total force = 0.000195 Total SCF correction = 0.000000
Total force = 0.000193 Total SCF correction = 0.000001
Total force = 0.000194 Total SCF correction = 0.000001
Total force = 0.000208 Total SCF correction = 0.000000
Total force = 0.000271 Total SCF correction = 0.000001
Total force = 0.000336 Total SCF correction = 0.000000
Total force = 0.000350 Total SCF correction = 0.000001
Total force = 0.000355 Total SCF correction = 0.000001
Total force = 0.000356 Total SCF correction = 0.000001
Total force = 0.000351 Total SCF correction = 0.000000
Total force = 0.000364 Total SCF correction = 0.000000
Total force = 0.000437 Total SCF correction = 0.000000
Total force = 0.000509 Total SCF correction = 0.000000
Total force = 0.000542 Total SCF correction = 0.000002
Total force = 0.000520 Total SCF correction = 0.000001
----------------------------------------------------------------------------
-------------
I also previously tried without ecfixed, qcutz, q2sigma options but the
force did not converge as well.
Any suggestions would be greatly appreciated.
Thank you.
Sincerely,
JISEOK KIM, Ph.D.
Postdoctoral Research Associate
Department of Materials Science and Engineering
University of Texas at Dallas
800 W. Campbell Rd. RL10
Richardson, TX 75080
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