<div dir="ltr">Dear all,<br><br>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.<br><br>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.<br><br>So far, I’ve tried several approaches to reduce Pulay stress and improve pressure convergence:<br>Increased the plane-wave cutoff energy to 80 Ry<br>Tested different values of the `nraise` parameter<br>Doubled the system size from 80 to 160 atoms to reduce finite-size effects<br>Switched the cell dynamics from `pr` (Parrinello-Rahman) to `w` (Wentzcovitch)<br><br>Unfortunately, neither change made much of a difference.  <br><br>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.<br><br>Seitaro Yazawa<br>graduate student<br>Department of Earth and Planetary science<br>Univ. Tokyo<br><br>&control<br> calculation = 'vc-md'<br> prefix='bridgmanite',<br> tstress = .true.<br> tprnfor = .true.<br> pseudo_dir = './pseudopotential',<br> outdir='./work/'<br> nstep = 2000<br> disk_io = 'low'<br>/<br>&system<br> ibrav = 0,<br> nat = 80,<br> ntyp = 3,<br> ecutwfc = 50.0,<br> ecutrho = 300.0,<br> occupations = 'smearing'<br> smearing = 'm-p'<br> degauss = 0.01<br> nosym=.true.<br>/<br>&electrons<br> mixing_beta = 0.7<br> conv_thr = 1.0d-5<br>/<br>&ions<br> ion_temperature = 'rescaling'<br> tempw = 300<br> nraise = 100<br> tolp = 10<br>/<br>&cell<br> cell_dynamics = 'pr'<br> press = 0<br> cell_dofree = 'xyz'<br>/<br>ATOMIC_SPECIES<br>Mg  24.3050  Mg.pbe-n-kjpaw_psl.0.3.0.UPF<br>Si  28.0855  Si.pbe-n-kjpaw_psl.0.1.UPF<br>O 15.9994  O.pbe-n-kjpaw_psl.0.1.UPF<br>ATOMIC_POSITIONS {angstrom}<br>Mg            2.4406190140        2.8727780929        1.7912494919<br>Mg            2.2985751016        2.3133781666        5.2791667246<br>Mg            0.0273236948        4.8015879094        5.2790920900<br>Mg            4.7118622874        0.3845670807        1.7913274731<br>Si            2.3696574944        0.1048379856        3.5349811056<br>Si           -0.0431827922        2.5930428386        3.5348865041<br>Si            2.3701118078        0.1051587079        0.0469825522<br>Si           -0.0427270638        2.5933628517        0.0468866746<br>O             0.4574649955        2.4187818519        1.7909459951<br>O             4.2817269017        2.7673678905        5.2794534229<br>O             2.8698492588        0.2790656557        5.2790494327<br>O             1.8693379325        4.9070854303        1.7913489149<br>O             0.9046391591        1.1080890629        3.9091481999<br>O             3.8345380314        4.0780493924        3.1612443211<br>O             3.3175234703        1.5897700456        3.1609566527<br>O             1.4216780631        3.5963710921        3.9094349151<br>O             3.8349023079        4.0783140121        0.4217844016<br>O             0.9042897177        1.1078570373        6.6486135341<br>O             1.4213168198        3.5961372909        6.6489013495<br>O             3.3178763085        1.5900331398        0.4214993183<br>Mg            2.4404920313        7.8493131424        1.7916867735<br>Mg            2.2984477893        7.2899133197        5.2796049409<br>Mg            0.0271958832        9.7781221425        5.2795281801<br>Mg            4.7117344667        5.3611022758        1.7917673172<br>Si            2.3695299095        5.0813727127        3.5354195251<br>Si           -0.0433095179        7.5695777251        3.5353244359<br>Si            2.3699848128        5.0816933874        0.0474207408<br>Si           -0.0428544923        7.5698980568        0.0473247647<br>O             0.4573382344        7.3953169875        1.7913838757<br>O             4.2815997612        7.7439030226        5.2798903481<br>O             2.8697220975        5.2556005826        5.2794877501<br>O             1.8692103937        9.8836201825        1.7917861676<br>O             0.9045124121        6.0846242720        3.9095867606<br>O             3.8344100864        9.0545842859        3.1616804575<br>O             3.3173964094        6.5663045400        3.1613943153<br>O             1.4215507207        8.5729058161        3.9098727744<br>O             3.8347744935        9.0548490078        0.4222203388<br>O             0.9041623873        6.0843919705        6.6490520691<br>O             1.4211889342        8.5726721918        6.6493389621<br>O             3.3177490881        6.5665680889        0.4219365496<br>Mg            7.2661922862        2.8729005183        1.7918781973<br>Mg            7.1241479156        2.3135000475        5.2797966105<br>Mg            4.8528971111        4.8017100807        5.2797191998<br>Mg            9.5374341106        0.3846897857        1.7919582511<br>Si            7.1952301259        0.1049601528        3.5356107047<br>Si            4.7823907743        2.5931650797        3.5355159865<br>Si            7.1956849345        0.1052803854        0.0476120992<br>Si            4.7828458328        2.5934859144        0.0475165040<br>O             5.2830388066        2.4189039164        1.7915756351<br>O             9.1072998173        2.7674905575        5.2800817677<br>O             7.6954218063        0.2791874890        5.2796787609<br>O             6.6949111801        4.9072082874        1.7919778694<br>O             5.7302124789        1.1082117321        3.9097781551<br>O             8.6601103499        4.0781718542        3.1618721902<br>O             8.1430960609        1.5898920689        3.1615854057<br>O             6.2472512603        3.5964934522        3.9100645206<br>O             8.6604748686        4.0784362283        0.4224119483<br>O             5.7298621237        1.1079791843        6.6492438340<br>O             6.2468898094        3.5962594572        6.6495309669<br>O             8.1434495420        1.5901546743        0.4221277399<br>Mg            7.2660647945        7.8494350617        1.7923164356<br>Mg            7.1240210483        7.2900354819        5.2802335548<br>Mg            4.8527690433        9.7782448177        5.2801590548<br>Mg            9.5373069524        5.3612249442        1.7923954629<br>Si            7.1951031891        5.0814951781        3.5360483545<br>Si            4.7822633044        7.5697007251        3.5359533136<br>Si            7.1955573199        5.0818158845        0.0480495453<br>Si            4.7827185818        7.5700205114        0.0479535633<br>O             5.2829109209        7.3954396459        1.7920125894<br>O             9.1071726756        7.7440252329        5.2805201016<br>O             7.6952949011        5.2557231584        5.2801163477<br>O             6.6947836454        9.8837420320        1.7924157976<br>O             5.7300855066        6.0847470591        3.9102149976<br>O             8.6599830605        9.0547066212        3.1623110983<br>O             8.1429695926        6.5664270556        3.1620236108<br>O             6.2471235521        8.5730278400        3.9105014290<br>O             8.6603472223        9.0549702547        0.4228505347<br>O             5.7297355413        6.0845146085        6.6496800132<br>O             6.2467619709        8.5727943058        6.6499680905<br>O             8.1463435811        6.5676263992        0.4211232920<br>CELL_PARAMETERS {angstrom}<br>   9.651145881   0.0   0.0<br>   0.0   9.953069617   0.0<br>   0.0   0.0    6.976003984<br>K_POINTS {automatic}<br>2 2 4 0 0 0</div>