[QE-users] No SCF convergence for simple actinide compounds

[Lorenzo Paulatto]

I wouldn't call an oxide of Plutonium "simple"... My guess is that it
becomes metallic in simple DFT, try to treat it as such, by setting
occupations="smearing"

Cheers

-- 
Lorenzo Paulatto

On Thu, 30 Jul 2020, 18:44 Sergei Butorin, <sergei.butorin at physics.uu.se>
wrote:

> I use QE 6.4.1 and have encountered a problem of pure or no-convergence in
> scf runs for simple actinide compounds. For example, for PuO2, I get quick
> convergence for a primitive cell but for a conventional unit cell the
> convergence to ‘poor’ conv_thr=1.1d-6 is reached only after 560 iterations
> with the same parameters and pseudos in the input file (see below):
>
>
>
> &control
>
>   calculation = 'scf'
>
>   verbosity='high'
>
>   prefix = 'system'
>
>   pseudo_dir = '/My_input/PuO2/'
>
>   outdir = './Out'
>
>   wfcdir = 'undefined'
>
>   tstress = .false.
>
>   tprnfor = .false.
>
> /
>
> &system
>
>     ibrav = 0
>
>   A =    5.39819
>
>     nat   = 12
>
>     ntyp  = 2
>
>   noncolin = .false.
>
>   lspinorb = .false.
>
>   ecutwfc = 50
>
>   ecutrho = 400
>
>   occupations = 'fixed'
>
>   nspin  = 1
>
> /
>
> &electrons
>
>   conv_thr = 1.1d-6
>
>   mixing_beta = 0.3
>
>   electron_maxstep = 2000
>
>   startingwfc = 'atomic+random'
>
>   diagonalization = 'david'
>
> /
>
> &ions
>
> /
>
> ATOMIC_SPECIES
>
> Pu   239.0522      Pu.pbe-spfn-rrkjus_psl.1.0.0.UPF
>
> O   15.9994        O.pbe-n-rrkjus_psl.1.0.0.UPF
>
> CELL_PARAMETERS alat
>
>   1.000000000000000   0.000000000000000   0.000000000000000
>
>   0.000000000000000   1.000000000000000   0.000000000000000
>
>   0.000000000000000   0.000000000000000   1.000000000000000
>
> ATOMIC_POSITIONS crystal
>
> Pu   0.000000000000000   0.000000000000000   0.000000000000000
>
> Pu   0.000000000000000   0.500000000000000   0.500000000000000
>
> Pu   0.500000000000000   0.000000000000000   0.500000000000000
>
> Pu   0.500000000000000   0.500000000000000   0.000000000000000
>
>  O   0.250000000000000   0.250000000000000   0.250000000000000
>
>  O   0.750000000000000   0.250000000000000   0.750000000000000
>
>  O   0.750000000000000   0.750000000000000   0.750000000000000
>
>  O   0.250000000000000   0.750000000000000   0.750000000000000
>
>  O   0.250000000000000   0.250000000000000   0.750000000000000
>
>  O   0.750000000000000   0.250000000000000   0.250000000000000
>
>  O   0.250000000000000   0.750000000000000   0.250000000000000
>
>  O   0.750000000000000   0.750000000000000   0.250000000000000
>
> K_POINTS automatic
>
> 2  2  2  1  1  1
>
>
>
> Things I have tried to improve the situation but without success:
>
>
>
> 1. Significantly increasing ecutwfc and ecutrho values and keeping the
> 10-12 ratio for US pseudos.
>
> 2. Using NC pseudos both from the sg15 collection and harder TM pseudos
> with smaller rc with appropriate ecutwfc and ecutrho values in my pw.x
> input.
>
> 3. Smaller mixing-beta down to 0.1.
>
> 4. Different mixing_mode (e.g. 'local-TF').
>
> 5. Different diagonalization ('cg').
>
>
>
> No wonder that in case of a supercell, the convergence value goes only
> down to a few Ry at best. The occupations = 'smearing' option does not help
> either.
>
>
>
> Similar problems I have encoutered for UO2, although I have not
> investigated that case in detail.
>
>
>
> My question is whether QE (pw.x) is generally so bad in handling the
> f-element systems or something is really wrong on my side.
>
>
>
> Dr. Sergei Butorin
>
> Uppsala University
>
> Sweden
>
>
>
>
>
>
>
>
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