[Pw_forum] Problems Computing Cholesky for VC-Relax of MnO2

[Lance Kavalsky]

Dear All,


I have tried the following changes to the system (see latest input file below), all of which still converge to the non-magnetic state regardless of starting magnetization:


  1.  Breaking the symmetry by treating the two O atoms as different species (the unit cell contains 1 Mn and 2 O)
  2.  Introducing the nbnd parameter into &system
  3.  Running the simulation with a finer k-mesh (21x21x7)
  4.  With and without the Hubbard correction
  5.  With and without using noncolin=.true.
  6.  And alternative pseudopotentials (namely Mn.pbe-spn-rrkjus_psl.0.3.1.UPF and O.pbe-rrkjus.upf.UPF)

Some papers mention that the ferromagnetism was observed, and others don't mention it at all.

I have approached the other members of my group as well to no avail.  I have been stuck with this for a month and would truly appreciate any advice or other suggestions you may have.

&control
    disk_io = 'high',
    calculation ='vc-relax',
    restart_mode = 'from_scratch'
    prefix = 'all',
    outdir = './all',
    Pseudo_dir = './'
    nstep=250,
/

&system
    lda_plus_u=.true.
    hubbard_U(1)= 3.9
    degauss                   =  1.00000e-02
    ecutrho                   =  2.25000e+02
    ecutwfc                   =  2.50000e+01
    ibrav                     = 0
    nat                       = 3
    nspin                     = 2
    ntyp                      = 3
    occupations               = "smearing"
    smearing                  = "gaussian"
    starting_magnetization(1) =  1.00000
    starting_magnetization(2) =  -0.60000e+00
    starting_magnetization(3) =  -0.60000e+00
    nbnd = 19



 /

 &electrons
    conv_thr         =  1.00000e-06
    electron_maxstep = 200
    mixing_beta      =  4.00000e-01
    startingpot      = "atomic"
    startingwfc      = "atomic+random"

/

 &ions
    ion_dynamics = 'bfgs'
 /

 &cell
    cell_factor=6.0,
    cell_dofree = '2Dxy',
 /


CELL_PARAMETERS {angstrom}

   2.240463696  -0.000000000   0.000000000
  -1.120231848   1.940298414   0.000000000
   0.000000000   0.000000000  17.431921826

ATOMIC_SPECIES

  Mn 54.9380  Mn.pbe-spn-rrkjus_psl.0.3.1.UPF
  O1  15.9994  O.pbe-n-kjpaw_psl.0.1.upf
  O2  15.9994  O.pbe-n-kjpaw_psl.0.1.upf

ATOMIC_POSITIONS {angstrom}

Mn       0.000000000   0.000000000   0.603503436
O1        1.120233376   0.646765629  -0.789807394
O2       -0.000000765   1.293533550   1.997300505



K_POINTS automatic
21 21 7 1 1 1



Thanks so much,

Lance Kavalsky
MASc student
Dept. of Materials Science and Engineering
University of Toronto

________________________________
From: pw_forum-bounces at pwscf.org <pw_forum-bounces at pwscf.org> on behalf of Lorenzo Paulatto <lorenzo.paulatto at impmc.upmc.fr>
Sent: Thursday, September 7, 2017 3:39:53 AM
To: pw_forum at pwscf.org
Subject: Re: [Pw_forum] Problems Computing Cholesky for VC-Relax of MnO2

On 06/09/17 21:01, Lance Kavalsky wrote:
> I am no longer getting the error after increasing the energy cutoff of
> the wavefunctions to 250.0 Ry, decreasing the smearing to 0.01, and
> resetting the diagonalization back to davidson.


You mean of the charge density cutoff?

> I have experimented with varying the starting magnetizations and it
> consistently converges to a non-magnetic state. However, M. Kan et al.
> showed that a ferromagnetic state should exist via DFT (J. Phys. Chem.
> Lett., *2013*, /4/ (20), pp 3382–3386). Is this lack of magnetic states
> in my investigations more likely a result of not yet discovering a
> suitable starting magnetization, or could there be another reason such
> as choice of pseudopotentials?
>
I do not know your system, but you may have to start with to different
species of Mg, in order to break symmetry. This is necessary if one of
the symmetries of your crystal send Mg1 to Mg2 changing its orientation.

Example:

      nat=4, ntyp=3,
...
    starting_magnetization(1)=0.5 !Mn1
    starting_magnetization(2)=0.5 !Mn2
    starting_magnetization(3)=-0.5 !Oxygen
...
  ATOMIC_SPECIES
   Mn1 54.9380  Mn.pbe-spn-kjpaw_psl.0.3.1.upf
   Mn2 54.9380  Mn.pbe-spn-kjpaw_psl.0.3.1.upf
   O  15.9994  O.pbe-n-kjpaw_psl.0.1.upf

ATOMIC_POSITIONS {angstrom}
Mn1       1.463698094   2.529784343   0.000006382
Mn2       2.923484801   0.001355102   1.898036230
O        0.003938199   1.686984261   0.949009435
O        1.463753969   0.844151693   2.847056902


[resending to list]

--
Dr. Lorenzo Paulatto
IdR @ IMPMC -- CNRS & Université Paris 6
phone: +33 (0)1 442 79822 / skype: paulatz
www:   http://www-int.impmc.upmc.fr/~paulatto/
mail:  23-24/423 Boîte courrier 115, 4 place Jussieu 75252 Paris Cédex 05
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