[QE-users] Large estimated SCF accuracy for monolayer \alpha-RuCl3

[Paolo Giannozzi]

On 6/21/23 07:29, Lingzhi ZHANG wrote:

> I’m conducting GGA+SOC+U+Constrained DFT in QE-7.0.

what do you mean by "constrained DFT" ?

> But the estimated SCF accuracy for my system is considerably large in the first and the following steps, more enormous than 10000 Ry.
> 
> I have tried many methods such as modifying the mixing scheme from plain to TF, tuning the degauss, and trying different occupation and smearing schemes.
> I also tried to start from the GGA+LSDA+U case, which works well and gets converged in 700 steps.
> But no scheme works for  GGA+SOC+U+Constrained DFT.
> And even for just the GGA+SOC+U case, I can't obtain a small SCF accuracy.

Are you sure DFT+U for SOC works with PAW potentials?

Paolo

> I’d like to know what I can do for it and get a normal SCF process.
> 
> My input is in the following.
> This structure was obtained from OpenMX, another DFT package based on the LCAO method.
> 
> &CONTROL
>      calculation='scf',
>      prefix='mono',
>      pseudo_dir='/home/zhang/calculation/rucl3/pseudo',
>      restart_mode='from_scratch',
>      outdir='./',
>      verbosity='high',
> /
> &SYSTEM
>      ibrav= 0,
>      nat= 16, ntyp= 3,
>      occupations = 'smearing',
>      smearing='mp', degauss=1d-9,
>      ecutwfc= 100,
>      noncolin=.true.,lspinorb=.true.,
>      starting_magnetization(1)= 0.5,
>      starting_magnetization(2)= 0.5,
>      starting_magnetization(3)= 0.0,
>      lda_plus_u = .true.,
>      lda_plus_u_kind = 1,
>      U_projection_type = 'ortho-atomic',
>      Hubbard_U(1)=1.5,
>      Hubbard_U(2)=1.5
> /
> &ELECTRONS
>      electron_maxstep = 1600
>      conv_thr = 1.0d-8
>      mixing_mode = 'TF'
>      mixing_beta = 4.0d-2
>      mixing_ndim = 20
>      startingpot = 'atomic'
>      diagonalization = 'david'
> 
> /
> ATOMIC_SPECIES
> Ruu     101.07       Ru.rel-pbe-spn-kjpaw_psl.1.0.0.UPF
> Rud     101.07       Ru.rel-pbe-spn-kjpaw_psl.1.0.0.UPF
> Cl      35.45        Cl.pbe-n-kjpaw_psl.1.0.0.UPF
> ATOMIC_POSITIONS {angstrom}
>      Ruu     -2.4165100      0.0119000      2.4251100
>      Ruu      0.0032200      0.0119000      0.0053700
>      Cl       2.3833500     -0.0499700      0.0334100
>      Cl      -2.3884800     -0.0499700      4.8052300
>      Cl      -0.0381100      0.0580100      2.3837700
>      Cl      -2.3751800     -0.0342100      0.0467100
>      Cl      -2.4518700     -2.3681500      2.5014800
>      Cl       0.0796000     -2.3681500     -0.0299800
>      Rud      0.0105400      2.4538100     -2.4511300
>      Rud      2.4302700      2.4538100     -4.8708700
>      Cl       4.8104000      2.3919400     -4.8428300
>      Cl       0.0385700      2.3919400     -0.0710100
>      Cl       2.3889400      2.4999200     -2.4924700
>      Cl       0.0518700      2.4077000     -4.8295300
>      Cl      -0.0248200      0.0737600     -2.3747600
>      Cl       2.5066500      0.0737600     -4.9062200
> CELL_PARAMETERS {angstrom}
>       4.8541000     4.8838200    -9.7524800
>      -4.8762300     2.4419100     2.4270500
>      10.0203300    10.0185400    10.0203300
> K_POINTS {automatic}
>   6 12 1 0 0 0
> 
> 
> 
> The following is part of the output
> total energy = -2977.28363823 Ry estimated scf accuracy < 529768.11044287 Ry
> total energy = -2977.28363823 Ry estimated scf accuracy < 529768.11044287 Ry
> total energy = -3184.06809008 Ry estimated scf accuracy < 814811.34802588 Ry
> total energy = -3274.94372181 Ry estimated scf accuracy < 746852.52429958 Ry
> total energy = -3307.21972156 Ry estimated scf accuracy < 752237.62011255 Ry
> total energy = -3291.26999775 Ry estimated scf accuracy < 757458.22549562 Ry
> total energy = -3349.60629608 Ry estimated scf accuracy < 765501.04417510 Ry
> total energy = -3337.49045478 Ry estimated scf accuracy < 768896.10678680 Ry
> total energy = -3287.13640144 Ry estimated scf accuracy < 762797.72531670 Ry
> total energy = -3333.32846680 Ry estimated scf accuracy < 751861.05720886 Ry
> total energy = -3341.65785225 Ry estimated scf accuracy < 754604.69881806 Ry
> total energy = -3350.72599779 Ry estimated scf accuracy < 749241.08182438 Ry
> total energy = -3366.01560869 Ry estimated scf accuracy < 741018.08470080 Ry
> 
> 
> 
> With best regards
> 
> Lingzhi Zhang
> Department of Applied Physics,
> University of Tokyo, Japan
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-- 
Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,
Univ. Udine, via delle Scienze 208, 33100 Udine Italy, +39-0432-558216