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I am noticing a possible convergence problem in a magnetic $U$ system I am studying. In the OSZICAR file I often see the rms(c) value go to about 0.2e+3 and stabilize. Can anyone suggest what may be wrong in my calculation that can cause this?

I suspect the mixing parameters are the issue and I have tried the defaults as well as the pseudolinear mixing suggested by VASP of AMIX=0.3, BMIX=0.001.

Here is the start of the OSZICAR output. I am working on tungsten oxides using the materials project default parameters in terms of $U$, pseudopotentials, and general energy cutoffs.

       N       E                     dE             d eps       ncg     rms          rms(c)
DAV:   1     0.996952880030E+03    0.99695E+03   -0.39229E+04  3360   0.140E+03
DAV:   2     0.420320154504E+02   -0.95492E+03   -0.89279E+03  3588   0.430E+02
DAV:   3    -0.925122529562E+02   -0.13454E+03   -0.13109E+03  3832   0.172E+02
DAV:   4    -0.981421469589E+02   -0.56299E+01   -0.55757E+01  3984   0.375E+01
DAV:   5    -0.983539220900E+02   -0.21178E+00   -0.21087E+00  5016   0.665E+00
DAV:   6    -0.983570555376E+02   -0.31334E-02   -0.31033E-02  4224   0.800E-01
DAV:   7    -0.983571847233E+02   -0.12919E-03   -0.12837E-03  4920   0.162E-01
DAV:   8    -0.983571860469E+02   -0.13235E-05   -0.13192E-05  2656   0.166E-02    0.662E+01
DAV:   9    -0.804838944016E+02    0.17873E+02   -0.44298E+01  4544   0.495E+01    0.381E+01
DAV:  10    -0.811208958861E+02   -0.63700E+00   -0.38276E+01  4936   0.568E+01    0.188E+03
DAV:  11    -0.814674048119E+02   -0.34651E+00   -0.42624E+00  3756   0.964E+00    0.188E+03
DAV:  12    -0.803474022983E+02    0.11200E+01   -0.27246E-01  4264   0.268E+00    0.184E+03
DAV:  13    -0.803447815420E+02    0.26208E-02   -0.15007E-02  3696   0.671E-01    0.184E+03
DAV:  14    -0.827481331115E+02   -0.24034E+01   -0.11705E+00  5324   0.101E+01    0.188E+03
DAV:  15    -0.830941535514E+02   -0.34602E+00   -0.19499E-01  4256   0.245E+00    0.188E+03
DAV:  16    -0.827076829935E+02    0.38647E+00   -0.19109E-01  4028   0.362E+00    0.188E+03
DAV:  17    -0.839071530160E+02   -0.11995E+01   -0.18920E+00  4072   0.775E+00    0.188E+03
DAV:  18    -0.852362012098E+02   -0.13290E+01   -0.19289E+00  4272   0.700E+00    0.188E+03
DAV:  19    -0.850163602711E+02    0.21984E+00   -0.43203E-01  3960   0.207E+00    0.188E+03
DAV:  20    -0.853790409329E+02   -0.36268E+00   -0.21727E+01  4452   0.694E+00
   1 F= -.85379041E+02 E0= -.85379041E+02  d E =-.853790E+02  mag=    -0.3688
quench:  g(F)=  0.000E+00 g(S)=  0.000E+00 dE (1.order)= 0.000E+00
 bond charge predicted
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    $\begingroup$ Others might be able to provide more insight if you add in what class of materials you're studying here, broadly speaking. $\endgroup$
    – Andrew Rosen
    Dec 30, 2020 at 6:56
  • $\begingroup$ @AndrewRosen I have included some extra details. My suspected fix of raising kpoints seems to have only slightly fixed the problem, I am still having trouble with this so I will be trying some of your suggestions on discord as well. $\endgroup$
    – Tristan Maxson
    Dec 30, 2020 at 18:41
  • $\begingroup$ @TristanMaxson Did you use LMAXMIX? For systems with d/f electrons when performing spin polarized +U calculations, you necessarily need to include LMAXMIX. $\endgroup$
    – Xivi76
    Jan 3, 2021 at 19:46
  • $\begingroup$ @TristanMaxson Are you using the W_pv POTCAR? That one is really dodgy (which is used in the Material Project) and was later removed in the PBE 54 set (cms.mpi.univie.ac.at/marsweb/index.php/news/36-highlights/…). From my experience using W_sv gives better convergence for the electronic loops. $\endgroup$
    – bzbzbz
    Apr 20, 2021 at 8:27
  • $\begingroup$ I am using the W_sv POTCAR not the W_pv, the W_pv POTCAR was almost completely unusable. $\endgroup$
    – Tristan Maxson
    Apr 20, 2021 at 11:52

1 Answer 1

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Judging by your initial energies, it looks like you're starting a calculation from scratch. I've had good luck so far converging spin-polarized calculations by first doing a non-spin-polarized calculation, writing the CHG, CHGCAR, and WAVECAR files, and using those to start a spin-polarized calculation. This is the recommended method if such calculations aren't converging reliably according to the wiki.

In addition, I've found ALGO=All to converge sometimes when the default doesn't.

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  • $\begingroup$ +1 Welcome to our community, and thank you for contributing this answer to a long-standing unanswered question! We hope to see much more of you in the future! I just made some slight edits that it might be helpful for you to look at. $\endgroup$
    – Nike Dattani
    Jun 23, 2021 at 18:32
  • $\begingroup$ Welcome, @Eric Taw! I just wanted to say I agree with your answer. :) $\endgroup$
    – Andrew Rosen
    Jun 24, 2021 at 2:43

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