Hi,
After doing a vc-relax calculation, I used the relaxed cell parameters and
coordinates to run a scf calculation with the same convergence criteria and
cutoffs. However, the system's stress and pressure are shown to be very
different. A similar issue I encountered on the QE forum, was fixed by
tweaking the convergence against the Ecut value. But before I even started
the computations, I verified convergence against Ecut and Kpoints. I have
used the NC PseudoDojo PP. Any assistance in this respect would be greatly
appreciated.
*Here is the output stress from the last step of vc-relax:*
total stress (Ry/bohr**3) (kbar) P=
0.01
0.00000007 -0.00000001 0.00000000 0.01 -0.00
0.00
-0.00000001 0.00000007 -0.00000001 -0.00 0.01
-0.00
0.00000000 -0.00000001 0.00000008 0.00 -0.00
0.01
*Here is the output stress from scf:*
total stress (Ry/bohr**3) (kbar) P=
-0.81
0.00000173 0.00001357 -0.00001496 0.26 2.00
-2.20
0.00001357 0.00000039 0.00000247 2.00 0.06
0.36
-0.00001496 0.00000247 -0.00001869 -2.20 0.36
-2.75
*vc-relax input:*
&CONTROL
calculation = 'vc-relax'
etot_conv_thr = 1.0000000000d-06
forc_conv_thr = 1.0000000000d-05
outdir = './out/'
restart_mode = "restart"
pseudo_dir =
'/home/ikharagpur/Desktop/Aritri/HAP_QE_NEW_FINAL/HAP/convergance/ecut'
tprnfor = .true.
tstress = .true.
verbosity = 'high'
nstep = 200
/
&SYSTEM
degauss = 7.3498618000d-03
ecutrho = 6.40000000000d+02
ecutwfc = 7.00000000000d+01
ibrav = 0
nat = 41
nosym = .false.
ntyp = 6
occupations = 'smearing'
smearing = 'cold'
/
&ELECTRONS
conv_thr = 1.000000000d-06
electron_maxstep = 200
mixing_beta = 4.0000000000d-01
/
&IONS
ion_dynamics = "bfgs"
/
&CELL
press_conv_thr = 2.0000000000d-01
/
ATOMIC_SPECIES
Ca 40.078 Ca.upf
Na 22.98977 Na.upf
C 12.01070 C.upf
O 15.99940 O.upf
P 30.973761 P.upf
F 18.99840 F.upf
ATOMIC_POSITIONS (angstrom)
Ca 4.9287293961 2.5312304672 -0.0636442378
Ca 4.9349185508 2.9027082111 3.5370417241
Ca -0.1577580449 5.2894025247 3.4702936429
Ca -0.0739768540 5.6370186571 6.8292427360
Ca 8.2864929497 1.8261397245 1.8328431870
Ca 2.2609502006 -0.0600744649 1.7143079190
Ca 2.5803500800 8.0301042324 5.1805666090
Ca 1.2884866870 2.1466631854 5.2813513288
Ca 3.5158951682 6.0372944022 1.5643802295
Na -3.4620658996 6.2795759096 5.1320586858
P 3.0867436650 4.9588322631 5.0692930838
P -2.6763991933 5.0837191424 1.6232868296
P 7.4815069785 2.9665452844 5.2783593876
P 3.6993356186 0.3106309483 5.0653678851
P 1.0698739046 7.9066715577 1.7873359347
C 1.2319164303 3.3343087228 1.7769185095
O 5.4234243858 4.2067912520 1.5295885888
O -0.6403864365 3.8380742071 5.3624856051
O -0.8563492736 6.9192183026 5.0299634841
O 5.4654395719 1.2958222863 1.8055312311
O 1.5979572302 5.3945572754 5.0209743070
O -1.3937275362 4.1855912819 1.6316785468
O 6.1807498417 3.8078762598 5.2946494123
O 5.0962113435 1.0053557461 5.0068747439
O -0.2479127385 7.1008839512 1.9479371612
O 3.2273831465 3.4634648722 5.5060881250
O -2.6816919427 5.9171673155 2.9218077268
O 7.4667745856 2.1504763747 3.9587589893
O 3.0395685571 0.7662604690 6.4089715877
O 1.6807850560 7.4400441153 0.4356710059
O 3.7496780255 5.0285541608 3.6678802859
O 7.4304843715 1.9745826851 6.4795274695
O -2.5490400608 6.0618753239 0.4335569310
O 2.1013955811 7.5530328240 2.8790462527
O 2.8601969330 0.8778458001 3.8781941654
O 3.7949586106 5.8956756067 6.0712536830
O 0.8670346278 3.0547681296 2.9882678476
O 1.1759918381 2.3994316994 0.8866049917
O 1.5424153852 4.5568348312 1.4666970156
F -0.0049782532 -0.1503358719 1.6561706198
F 0.1059848801 0.2892097568 5.0465194963
K_POINTS automatic
2 2 3 0 0 0
CELL_PARAMETERS {angstrom}
9.397300 0.000000 0.000000
-4.698650 8.138301 0.000000
0.000000 0.000000 6.878200
*SCF input:*
&CONTROL
calculation = 'scf'
etot_conv_thr = 1.0000000000d-06
forc_conv_thr = 1.0000000000d-05
outdir = './out/'
restart_mode = "restart"
pseudo_dir =
'/home/ikharagpur/Desktop/Aritri/HAP_QE_NEW_FINAL/HAP/convergance/ecut'
tprnfor = .true.
tstress = .true.
verbosity = 'high'
nstep = 200
/
&SYSTEM
degauss = 7.3498618000d-03
ecutrho = 6.40000000000d+02
ecutwfc = 7.00000000000d+01
ibrav = 0
nat = 41
nosym = .false.
ntyp = 6
occupations = 'smearing'
smearing = 'cold'
/
&ELECTRONS
conv_thr = 1.000000000d-06
electron_maxstep = 200
mixing_beta = 4.0000000000d-01
/
&IONS
ion_dynamics = "bfgs"
/
&CELL
press_conv_thr = 2.0000000000d-01
/
ATOMIC_SPECIES
Ca 40.078 Ca.upf
Na 22.98977 Na.upf
C 12.01070 C.upf
O 15.99940 O.upf
P 30.973761 P.upf
F 18.99840 F.upf
CELL_PARAMETERS (angstrom)
9.403522322 0.089346951 -0.122107790
-4.624574075 8.051846973 0.082501283
-0.089342394 0.017896376 6.858790895
ATOMIC_POSITIONS (angstrom)
Ca 4.9770967179 2.5653460075 -0.1337751051
Ca 4.9372354934 2.9499612895 3.4521186383
Ca -0.2034442691 5.2530858364 3.4846530148
Ca -0.1137416011 5.6308719994 6.8378219159
Ca 8.2977611076 1.8800297962 1.7736446849
Ca 2.2413533700 -0.0004311837 1.6492932113
Ca 2.5998562512 8.0245043365 5.1748616941
Ca 1.2506199411 2.1667262606 5.2671066291
Ca 3.5541793955 6.0330065573 1.5227272245
Na -3.4956016665 6.2398706047 5.1457184840
P 3.0566889679 4.9793535438 5.0167609882
P -2.6527279052 5.0483379029 1.6427735806
P 7.4441823231 3.0411198798 5.2001935411
P 3.6424844026 0.3624968438 4.9862395101
P 1.1282750360 7.8820131992 1.8006951844
C 1.2510149622 3.3000132805 1.7883657663
O 5.4429703417 4.2737740659 1.4446893386
O -0.6738195196 3.8099927194 5.4003635803
O -0.8628277153 6.8847306005 5.0381510390
O 5.4357139734 1.3538452729 1.7347050153
O 1.5682645853 5.4071648285 4.9732803722
O -1.3803282481 4.1392385455 1.6342972619
O 6.1476486660 3.8856145701 5.2283043788
O 5.0436443940 1.0499318227 4.9116948440
O -0.1813703769 7.0691733500 1.9897343088
O 3.1868368926 3.4940352445 5.4742190961
O -2.6384743048 5.8674555732 2.9521034467
O 7.4112431425 2.2431045948 3.8687306171
O 2.9998260819 0.8176325894 6.3372934848
O 1.7154095157 7.4080787828 0.4394134783
O 3.7349447320 5.0315628428 3.6206036999
O 7.3859083710 2.0358197649 6.3901175611
O -2.5132765701 6.0348969987 0.4629313985
O 2.1946381316 7.5655991791 2.8668076838
O 2.7966145386 0.9308171326 3.8087744773
O 3.7629853133 5.9368419567 6.0029497429
O 0.8283603096 3.0530829701 2.9898800237
O 1.2402701808 2.3363280977 0.9260179599
O 1.5764439696 4.5094877888 1.4558604255
F -0.0267498884 -0.1708338921 1.6329080094
F 0.0483918544 0.3169071048 5.0200898238
K_POINTS automatic
2 2 3 0 0 0
Regards,
Aritri Roy
Junior Research Fellow,
Indian Institute of Technology Kharagpur
West Bengal, India
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