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