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ionic iterations are taking too many steps to converge

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ionic iterations are taking too many steps to converge

Posted: Fri Nov 01, 2024 6:45 am
by rudrabanerjee

Hi,
I am trying to optimize a system with two metal-porphyrin stacked top of each other. The electronic iterations are solving within 10-12 steps, but ionic iterations are taking too long, some times not converged with 500 steps.
A snippet from OSZICAR:

Code: Select all

      N       E                     dE             d eps       ncg     rms          rms(c)
RMM:   1    -0.118835676046E+04   -0.12411E-03   -0.46091E-02   680   0.343E-01
RMM:   2    -0.118835695061E+04   -0.19015E-03   -0.19245E-03   680   0.778E-02
RMM:   3    -0.118835697905E+04   -0.28441E-04   -0.26905E-04   680   0.333E-02
RMM:   4    -0.118835698813E+04   -0.90793E-05   -0.79069E-05   680   0.225E-02
RMM:   5    -0.118835699513E+04   -0.70015E-05   -0.63853E-05   979   0.139E-02
RMM:   6    -0.118835699622E+04   -0.10913E-05   -0.99043E-06   810   0.773E-03    0.631E-02
RMM:   7    -0.118835694803E+04    0.48195E-04   -0.31954E-05   948   0.829E-03    0.452E-02
RMM:   8    -0.118835692895E+04    0.19079E-04   -0.99987E-05  1269   0.141E-02    0.188E-02
RMM:   9    -0.118835693292E+04   -0.39716E-05   -0.17671E-05   839   0.151E-02
 180 F= -.11978284E+04 E0= -.11976149E+04  d E =-.884220E-04  mag=    -0.0413
       N       E                     dE             d eps       ncg     rms          rms(c)
RMM:   1    -0.118835685677E+04    0.72183E-04   -0.47046E-03   680   0.109E-01
RMM:   2    -0.118835687630E+04   -0.19538E-04   -0.19711E-04   680   0.262E-02
RMM:   3    -0.118835687943E+04   -0.31240E-05   -0.28198E-05   680   0.136E-02
RMM:   4    -0.118835688074E+04   -0.13160E-05   -0.11109E-05   680   0.819E-03
RMM:   5    -0.118835688137E+04   -0.62155E-06   -0.53273E-06   724   0.595E-03
RMM:   6    -0.118835688169E+04   -0.32577E-06   -0.28266E-06   683   0.376E-03    0.199E-02
RMM:   7    -0.118835687464E+04    0.70506E-05   -0.42176E-06   713   0.366E-03
 181 F= -.11978284E+04 E0= -.11976150E+04  d E =-.118372E-03  mag=    -0.0413
       N       E                     dE             d eps       ncg     rms          rms(c)
RMM:   1    -0.118835674986E+04    0.13183E-03   -0.51718E-03   680   0.116E-01
RMM:   2    -0.118835677062E+04   -0.20759E-04   -0.20988E-04   680   0.262E-02
RMM:   3    -0.118835677370E+04   -0.30760E-05   -0.28337E-05   680   0.132E-02
RMM:   4    -0.118835677493E+04   -0.12318E-05   -0.10501E-05   680   0.786E-03
RMM:   5    -0.118835677555E+04   -0.61741E-06   -0.53253E-06   709   0.573E-03
RMM:   6    -0.118835677586E+04   -0.30627E-06   -0.26793E-06   598   0.354E-03    0.235E-02
RMM:   7    -0.118835676987E+04    0.59870E-05   -0.31433E-06   693   0.323E-03
 182 F= -.11978284E+04 E0= -.11976150E+04  d E =-.110861E-03  mag=    -0.0413

Also, dE is oscillating between the energies:

Code: Select all

grep "F= " OSZICAR |tail -20
 169 F= -.11978279E+04 E0= -.11976144E+04  d E =-.119905E-03  mag=    -0.0414
 170 F= -.11978280E+04 E0= -.11976145E+04  d E =-.813772E-04  mag=    -0.0414
 171 F= -.11978280E+04 E0= -.11976146E+04  d E =-.101769E-03  mag=    -0.0413
 172 F= -.11978281E+04 E0= -.11976146E+04  d E =-.634526E-04  mag=    -0.0413
 173 F= -.11978281E+04 E0= -.11976147E+04  d E =-.797451E-04  mag=    -0.0412
 174 F= -.11978282E+04 E0= -.11976148E+04  d E =-.535342E-04  mag=    -0.0411
 175 F= -.11978282E+04 E0= -.11976148E+04  d E =-.656353E-04  mag=    -0.0411
 176 F= -.11978282E+04 E0= -.11976149E+04  d E =-.797392E-04  mag=    -0.0411
 177 F= -.11978283E+04 E0= -.11976150E+04  d E =-.882961E-04  mag=    -0.0412
 178 F= -.11978283E+04 E0= -.11976150E+04  d E =-.100299E-03  mag=    -0.0412
 179 F= -.11978283E+04 E0= -.11976150E+04  d E =-.705323E-04  mag=    -0.0412
 180 F= -.11978284E+04 E0= -.11976149E+04  d E =-.884220E-04  mag=    -0.0413
 181 F= -.11978284E+04 E0= -.11976150E+04  d E =-.118372E-03  mag=    -0.0413
 182 F= -.11978284E+04 E0= -.11976150E+04  d E =-.110861E-03  mag=    -0.0413
 183 F= -.11978284E+04 E0= -.11976150E+04  d E =-.505926E-04  mag=    -0.0413
 184 F= -.11978284E+04 E0= -.11976149E+04  d E =-.644235E-04  mag=    -0.0412
 185 F= -.11978284E+04 E0= -.11976149E+04  d E =-.639148E-04  mag=    -0.0412
 186 F= -.11978284E+04 E0= -.11976150E+04  d E =-.629038E-04  mag=    -0.0412
 187 F= -.11978284E+04 E0= -.11976149E+04  d E =-.647663E-04  mag=    -0.0412
 188 F= -.11978285E+04 E0= -.11976149E+04  d E =-.206955E-04  mag=    -0.0412

I am using the INCAR:

Code: Select all

AMIX = 0.200000
AMIX_MAG = 0.800000
BMIX = 0.000100
BMIX_MAG = 0.400000
POTIM = 0.050000
SIGMA = 0.200000
EDIFF = 1.00e-05
EDIFFG = -1.00e-02
ALGO = Veryfast
IBRION = 2
ISIF = 2
ISMEAR = 0
LORBIT = 11
NELM = 100
NELMDL = 6
NPAR = 10
NSW = 200
IVDW = 10
LPLANE = .TRUE.
LWAVE = .FALSE.
LCHARGE = .TRUE.
LREAL = Auto
LDAU = .TRUE.
LDAUL = -1 2 -1 -1
LDAUU = 0.000 5.000 0.000 0.000
LDAUJ = 0.000 1.000 0.000 0.000
ISPIN = 2
MAGMOM = 112*0.0000 1*3.0000 1*-3.0000 32*0.0000

I am unable to add POSCAR as attachment, so kindly excuse me to include 200 lines of POSCAR here.

Code: Select all

C  Fe H  N 
 1.0000000000000000
    14.7922763824000008    0.0000000000000000    0.0000000000000000
    -0.0000034116000000   12.8104906082000003    0.0000000000000000
     0.0000000000000000    0.0000000000000000   20.0000000000000000
 C   Fe  H   N  
 112   2  24   8
Cartesian
  0.0000000000000000  0.0000000000000000  9.7482548096140871
 13.5595864089999694  2.1350818319999707  9.7501537573283183
 12.3268955539999503  4.2701636630000435  9.7305111045375874
 11.0942055809999989  6.4052453039999637  9.6948737060110552
  9.8615156079999498  8.5403273269999858  9.6527026203297588
  8.6288247529999786 10.6754085859999890  9.6017394135689109
  7.3961381909999853  0.0000000000000000  9.5923262588449436
  2.4653794710000088  0.0000000000000000  9.7202883803944999
  1.2326891670000475  2.1350818319999707  9.7522654522510255
 -0.0000011370000186  4.2701636630000435  9.7631082393050690
 13.5595852719999996  6.4052453039999637  9.7453721198664951
 12.3268944170000374  8.5403273269999858  9.7127849991634765
 11.0942044439999794 10.6754085859999890  9.6751291713416538
  9.8615178819999851  0.0000000000000000  9.6386775048952860
  4.9307589410000450  0.0000000000000000  9.6445251512994421
  3.6980685269999833  2.1350818319999707  9.6982800640767781
  2.4653783330000181  4.2701636630000435  9.7322831577384612
  1.2326880290000022  6.4052453039999637  9.7451143159613469
 -0.0000022740000359  8.5403273269999858  9.7476676405786744
 13.5595841349999802 10.6754085859999890  9.7367458017677322
 12.3268966909999698  0.0000000000000000  9.7170695237054385
  6.1634477770000275  2.1350818319999707  9.6233277356678819
  4.9307578040000273  4.2701636630000435  9.6705695758374830
  3.6980673900000149  6.4052453039999637  9.6911255405219769
  2.4653771959999990  8.5403273269999858  9.7133047430215509
  1.2326868919999801 10.6754085859999890  9.7375860225719215
  8.6288270269999678  2.1350818319999707  9.6157628132363779
  7.3961370539999667  4.2701636630000435  9.6367610421450252
  6.1634466399999557  6.4052453039999637  9.6594038903458639
  4.9307566670000087  8.5403273269999858  9.6506654139338384
  3.6980662529999950 10.6754085859999890  9.6768116118772323
 11.0942067179999686  2.1350818319999707  9.6915660742342933
  9.8615167449999674  4.2701636630000435  9.6648990134529917
  8.6288258899999999  6.4052453039999637  9.6607478974324135
  7.3961359169999481  8.5403273269999858  9.6275454213320923
  6.1634455030000375 10.6754085859999890  9.6024949173966476
 -0.0000003789999996  1.4233885240000335  9.7550458349603897
 13.5595860300000179  3.5584701649999548  9.7542217586786482
 12.3268951749999509  5.6935521869999866  9.7258601786135603
 11.0942052019999995  7.8286338279999983  9.6859230942789907
  9.8615152290000534  9.9637158510000194  9.6371201498721621
  8.6288243739999775 12.0987971100000227  9.6007778855224153
  7.3961378119999841  1.4233885240000335  9.6005431707817817
  2.4653790910000355  1.4233885240000335  9.7275810659686162
  1.2326887879999939  3.5584701649999548  9.7560185002350082
 -0.0000015160000182  5.6935521869999866  9.7579554782279843
 13.5595848930000002  7.8286338279999983  9.7398595969418693
 12.3268940380000380  9.9637158510000194  9.7120087326977149
 11.0942040649999782 12.0987971100000227  9.6782121856329955
  9.8615175029999858  1.4233885240000335  9.6454024651328591
  4.9307585620000438  1.4233885240000335  9.6540401011392234
  3.6980681480000346  3.5584701649999548  9.7017454257796842
  2.4653779540000178  5.6935521869999866  9.7239830719727074
  1.2326876500000026  7.8286338279999983  9.7407777017606971
 -0.0000026530000370  9.9637158510000194  9.7460819874016060
 13.5595837559999790 12.0987971100000227  9.7379361233663939
 12.3268963119999686  1.4233885240000335  9.7236634108591335
  6.1634473979999722  3.5584701649999548  9.6384217454263670
  4.9307574250000270  5.6935521869999866  9.6725554966878953
  3.6980670110000156  7.8286338279999983  9.6829910386629603
  2.4653768169999992  9.9637158510000194  9.7134262822782436
  1.2326865129999804 12.0987971100000227  9.7392253545974885
  8.6288266480000164  3.5584701649999548  9.6326855130783358
  7.3961366749999664  5.6935521869999866  9.6541619696706107
  6.1634462609999563  7.8286338279999983  9.6452034660472119
  4.9307562880000084  9.9637158510000194  9.6372683922729188
  3.6980658739999939 12.0987971100000227  9.6822694123904327
 11.0942063390000172  3.5584701649999548  9.6963623133121040
  9.8615163659999663  5.6935521869999866  9.6730934289208736
  8.6288255109999987  7.8286338279999983  9.6475399641410284
  7.3961355380000526  9.9637158510000194  9.5975366960966184
  6.1634451240000381 12.0987971100000227  9.6033896307761797
  6.4572500000000410  4.1652500000000172 12.9402747604089736
  6.9250500000000104  2.8367500000000123 12.7187026312998448
  8.2834500000000233  2.8687500000000075 12.7170910969469890
  8.6879499999999883  4.2174500000000297 12.9382677920899489
 10.0094499999999975  4.6349499999999697 12.9750979715422119
 10.3987499999999660  5.9757499999999837 13.0363897144419543
 11.7955500000000217  6.4313500000000312 12.9615849151717271
 11.7597500000000430  7.7817499999999811 12.9349266258479094
 10.3404499999999686  8.1629499999999844 12.9957014667414974
  9.8822499999999458  9.4812499999999691 12.9052878660408599
  8.5425500000000500  9.8347500000000085 12.8560547968679835
  8.0749499999999674 11.1632500000000139 12.6567660353520921
  6.7164499999999592 11.1312500000000174 12.6560539414694126
  6.3117499999999760  9.7823499999999672 12.8564074151487056
  4.9903499999999861  9.3650499999999646 12.9110285440435923
  4.6013500000000471  8.0241499999999810 13.0070205870072702
  3.2044500000000347  7.5684499999999657 12.9546520688569053
  3.2401500000000043  6.2183500000000151 12.9796480185980165
  4.6595500000000483  5.8369499999999821 13.0474253979860073
  5.1177499999999778  4.5183499999999990 12.9820462093595861
  6.4572500000000410  4.1652500000000172 16.4983977641126458
  6.9250500000000104  2.8367500000000119 16.2651115214223871
  8.2834500000000233  2.8687500000000075 16.2674162747646243
  8.6879499999999883  4.2174500000000297 16.5013507370162671
 10.0094499999999975  4.6349499999999697 16.5892372954476670
 10.3987499999999660  5.9757499999999837 16.6728249836560671
 11.7955500000000217  6.4313500000000312 16.6826016265659511
 11.7597500000000430  7.7817499999999811 16.6464322340567428
 10.3404499999999686  8.1629499999999844 16.6193671304224964
  9.8822499999999458  9.4812499999999691 16.4995512372646367
  8.5425500000000500  9.8347500000000085 16.4103050195573843
  8.0749499999999674 11.1632500000000139 16.1881529872680225
  6.7164499999999592 11.1312500000000174 16.1919865837504702
  6.3117499999999760  9.7823499999999672 16.4163423460696976
  4.9903499999999861  9.3650499999999646 16.5140083168225544
  4.6013500000000471  8.0241499999999810 16.6348027515445160
  3.2044500000000342  7.5684499999999657 16.6688146637545316
  3.2401500000000043  6.2183500000000151 16.6984274528864738
  4.6595500000000483  5.8369499999999821 16.6788959279237083
  5.1177499999999778  4.5183499999999990 16.5881295008070353
  7.4782000000000233  7.0652400000000215 13.1954980498248027
  7.4782000000000233  7.0652400000000215 16.6145119111170452
  6.3113500000000391  1.9480500000000383 12.5794074046332298
  8.9383500000000087  2.0100500000000143 12.5740601872288167
  4.3839500000000440  3.7259500000000121 12.8844623013091564
 10.7820500000000035  3.8803500000000000 12.8760588047117164
 12.6778499999999958  5.8086500000000205 12.9012715303994892
 12.6079500000000220  8.4501500000000167 12.8485407214800631
 10.6161500000000224 10.2735499999999860 12.8007256257437358
  8.6886500000000435 12.0519499999999873 12.5306700303358927
  6.0616499999999709 11.9899500000000128 12.5278020545814854
  4.2177500000000467 10.1197499999999945 12.8075969668868197
  2.3221499999999549  8.1911499999999755 12.8702602157793660
  2.3921499999999507  5.5498500000000091 12.9218403979563927
  6.3113500000000391  1.9480500000000385 16.1207228236688813
  8.9383500000000087  2.0100500000000148 16.1253137354590024
  4.3839500000000440  3.7259500000000121 16.5212127595511546
 10.7820500000000035  3.8803500000000000 16.5242002648268098
 12.6778499999999958  5.8086500000000205 16.6897997405231777
 12.6079500000000220  8.4501500000000167 16.6152996602523118
 10.6161500000000224 10.2735499999999860 16.4155923443104257
  8.6886500000000435 12.0519499999999873 16.0499153606981473
  6.0616499999999709 11.9899500000000128 16.0565778907649985
  4.2177500000000467 10.1197499999999945 16.4371625697792858
  2.3221499999999553  8.1911499999999755 16.6470954961230575
  2.3921499999999503  5.5498500000000091 16.7075154183910257
  7.5537500000000435  4.9980500000000356 13.0653078651222074
  9.6068500000000174  7.0490499999999550 13.0892610708194130
  7.4461500000000163  9.0017499999999622 12.9660798112529143
  5.3928500000000517  6.9507500000000420 13.0965123687179759
  7.5537500000000435  4.9980500000000356 16.6224618479842619
  9.6068500000000174  7.0490499999999550 16.6564467604266824
  7.4461500000000163  9.0017499999999622 16.5298594843853515
  5.3928500000000517  6.9507500000000420 16.6617387848485201

Any help in making the convergence faster will be helpful.

Re: ionic iterations are taking too many steps to converge

Posted: Mon Nov 04, 2024 7:10 am
by jonathan_lahnsteiner2

Dear rudrabanerjee,

You have a rather complicated planar structure. You could try to optimize your structure by using Selective Dynamics. With selective dynamics you can prevent your layer of carbon atoms to move out of plane. Or you can do the optimization step wise to first optimize your structure in plane, then out of plane and so on. Selective dynamics is described on the vasp wiki on the POSCAR page. To use selective dynamics add a line Selective Dynamics after the ion specification into your POSCAR file as follows

Code: Select all

C  Fe H  N 
 1.0000000000000000
    14.7922763824000008    0.0000000000000000    0.0000000000000000
    -0.0000034116000000   12.8104906082000003    0.0000000000000000
     0.0000000000000000    0.0000000000000000   20.0000000000000000
 C   Fe  H   N  

 112   2  24   8
 Selective dynamics
Cartesian

Now every atom in your POSCAR file gets three additional logical entries. T or F for true or false. Like this for example

Code: Select all

0.0000000000000000  0.0000000000000000  9.7482548096140871 T T F

This would allow this atom to move along x and y direction but not in the z direction during optimization. Using this approach should simplify your optimization problem and increase convergence with respect to the ionic degrees of freedom. Another option would be to just keep all ionic degrees of freedom and increase NSW in your INCAR file or reduce the accuracy of the stopping criterion for the ionic relaxation.

All the best Jonathan

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