[QE-users] vc-relax Convergence problem with 'TS' VdW correction
Hooman Yaghoobnejad Asl
hynr8 at mst.edu
Fri Oct 12 16:36:20 CEST 2018
Dear all,
I'm experiencing a problem with total force minimization when the vdw_corr
= 'TS' is used. Without the vdw_corr option, force minimization completes
smoothly, as shown below:
Total force = 0.144455 Total SCF correction = 0.002938
Total force = 0.096620 Total SCF correction = 0.004258
Total force = 0.023833 Total SCF correction = 0.000694
Total force = 0.013572 Total SCF correction = 0.000196
Total force = 0.013176 Total SCF correction = 0.000775
Total force = 0.013520 Total SCF correction = 0.001316
Total force = 0.013322 Total SCF correction = 0.000670
Total force = 0.013164 Total SCF correction = 0.000897
Total force = 0.013634 Total SCF correction = 0.000800
Total force = 0.016822 Total SCF correction = 0.000639
Total force = 0.015558 Total SCF correction = 0.000354
Total force = 0.012359 Total SCF correction = 0.000858
Total force = 0.009014 Total SCF correction = 0.000322
Total force = 0.007140 Total SCF correction = 0.000338
Total force = 0.006073 Total SCF correction = 0.000556
Total force = 0.005047 Total SCF correction = 0.000465
Total force = 0.004639 Total SCF correction = 0.000050
Total force = 0.003113 Total SCF correction = 0.000382
Total force = 0.002225 Total SCF correction = 0.000268
Total force = 0.001698 Total SCF correction = 0.000156
Total force = 0.001505 Total SCF correction = 0.000372
Total force = 0.001422 Total SCF correction = 0.000244
Total force = 0.001442 Total SCF correction = 0.000420
However, after implementing the VdW correction, it seems that the forces
cannot be minimized further even after 200 ionic steps:
Total force = 0.146620 Total SCF correction = 0.003488
Total force = 0.108842 Total SCF correction = 0.004843
Total force = 0.069519 Total SCF correction = 0.000923
Total force = 0.016339 Total SCF correction = 0.002655
Total force = 0.015353 Total SCF correction = 0.001041
Total force = 0.016188 Total SCF correction = 0.000361
Total force = 0.016350 Total SCF correction = 0.000832
Total force = 0.015878 Total SCF correction = 0.001654
Total force = 0.016273 Total SCF correction = 0.000560
Total force = 0.016349 Total SCF correction = 0.000406
Total force = 0.015879 Total SCF correction = 0.001403
.
.
.
.
Total force = 0.015866 Total SCF correction = 0.001214
Total force = 0.016279 Total SCF correction = 0.000263
Total force = 0.016351 Total SCF correction = 0.000394
Total force = 0.015879 Total SCF correction = 0.000394
Total force = 0.016277 Total SCF correction = 0.001323
Total force = 0.016347 Total SCF correction = 0.000194
Total force = 0.015878 Total SCF correction = 0.000606
I was wondering if anyone can make a comment on this? I'm using QE 6.2 on a
cluster. Input copied below:
&CONTROL
title = 'Li0.5NiO2 NCPP FM VdW ' ,
calculation = 'vc-relax' ,
max_seconds = 86300 ,
! wf_collect = .true. ,
outdir = '/' ,
wfcdir = '/' ,
pseudo_dir = '/scratch/05246/pseudo/' ,
! restart_mode = 'restart' ,
prefix = 'LNO' ,
disk_io = 'low' ,
verbosity = 'high' ,
nstep = 200 ,
/
&SYSTEM
ibrav = 0,
celldm(1) = 1.889726,
nat = 21,
ntyp = 3,
ecutwfc = 80 ,
ecutrho = 320 ,
occupations = 'smearing' ,
degauss = 0.001 ,
smearing = 'gaussian' ,
nspin = 2 ,
starting_magnetization(1) = 0.25,
vdw_corr = 'TS' ,
/
&ELECTRONS
electron_maxstep = 500,
conv_thr = 1.0d-6 ,
/
&IONS
/
&CELL
/
CELL_PARAMETERS {alat}
5.790000 0.000000 0.000000
-1.447500 2.507144 0.000000
0.000000 0.000000 14.221000
ATOMIC_SPECIES
Ni 58.69000 Ni_ONCV_PBE-1.0.upf
O 15.99000 O_ONCV_PBE-1.0.upf
Li 6.94000 Li_ONCV_PBE-1.0.upf
ATOMIC_POSITIONS crystal
O 0.000000 0.000000 0.232000
O 0.000000 0.000000 0.768000
O 0.333333 0.333333 0.565333
O 0.333333 0.333333 0.101333
O 0.166667 0.666667 0.898667
O 0.166667 0.666667 0.434667
Ni 0.000000 0.000000 0.500000
Ni 0.333333 0.333333 0.833333
Ni 0.166667 0.666667 0.166667
Li 0.166667 0.666667 0.666667
O 0.500000 0.000000 0.232000
O 0.500000 0.000000 0.768000
O 0.833333 0.333333 0.565333
O 0.833333 0.333333 0.101333
O 0.666667 0.666667 0.898667
O 0.666667 0.666667 0.434667
Ni 0.500000 0.000000 0.500000
Ni 0.833333 0.333333 0.833333
Ni 0.666667 0.666667 0.166667
Li 0.500000 0.000000 0.000000
Li 0.833333 0.333333 0.333333
K_POINTS automatic
4 8 2 0 0 0
Thank you
P.S. I benchmarked the wf cut-off energy vs binary oxides for each metal
and 80 Ry gave values comparable to 320 Ry.
--
*Hooman Yaghoobnejad*
*PhD, Department of Chemistry*
*Missouri University of Science and Technology*
*Rolla, MO 65409*
*USA*
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