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Convergence issue of CoFe/MgO/CoFe sytem (MTJ)
Date: 2013/02/25 16:02
Name: H.Park

Deal all,

I'm trying to calculate TMR of the CoFe/MgO/CoFe system with Ta impurity.
But there is convergence issue.

=============================================================
Result ==>
NormRD is increasing... divergence?

SCF= 20 NormRD= 1.647053477238 Uele= 0.000000000000
SCF= 21 NormRD= 1.676406045321 Uele= 0.000000000000
SCF= 22 NormRD= 1.676412340739 Uele= 0.000000000000
SCF= 23 NormRD= 1.676725895313 Uele= 0.000000000000
SCF= 24 NormRD= 1.677190501001 Uele= 0.000000000000
SCF= 25 NormRD= 1.677776807414 Uele= 0.000000000000
SCF= 26 NormRD= 1.678466279148 Uele= 0.000000000000
SCF= 27 NormRD= 1.679246622603 Uele= 0.000000000000

................

SCF= 493 NormRD= 3.615303112751 Uele= 0.000000000000
SCF= 494 NormRD= 3.618440750586 Uele= 0.000000000000
SCF= 495 NormRD= 3.621578500813 Uele= 0.000000000000
SCF= 496 NormRD= 3.624716306382 Uele= 0.000000000000
SCF= 497 NormRD= 3.627854101348 Uele= 0.000000000000
SCF= 498 NormRD= 3.630991812132 Uele= 0.000000000000
SCF= 499 NormRD= 3.634129358923 Uele= 0.000000000000
SCF= 500 NormRD= 3.637266657161 Uele= 0.000000000000


=====================================================
Here is my input file.


NEGF.Num.Poles 100 # defalut=150
NEGF.scf.Kgrid 6 6 # defalut=1 1

NEGF.bias.voltage 0.0 # default=0.0 (eV)
NEGF.bias.neq.im.energy 0.01 # default=0.01 (eV)
NEGF.bias.neq.energy.step 0.02 # default=0.02 (eV)

Dos.fileout off # on|off, default=off
NEGF.Dos.energyrange -15.0 25.0 5.0e-3 #default=-10.0 10.0 5.0e-3 (eV)
NEGF.Dos.energy.div 200 # default=200
NEGF.Dos.Kgrid 1 1 # default=1 1

NEGF.tran.energydiv 200 # default=200
NEGF.tran.energyrange -10 10 1.0e-3 # default=-10.0 10.0 1.0e-3 (eV)
NEGF.tran.Kgrid 72 72 # default= 1 1

Species.Number 5
<Definition.of.Atomic.Species
Co Co6.0S-s2p3d2f1 Co_PBE11S
Fe Fe6.0H-s2p2d1 Fe_PBE11H
Mg Mg7.0-s2p2 Mg_PBE11
O O5.0-s2p2d1 O_PBE11
Ta Ta7.0-s3p3d3f1 Ta_PBE11
Definition.of.Atomic.Species>

#
# Atoms
#

Atoms.SpeciesAndCoordinates.Unit Ang # Ang|AU

Atoms.Number 25
<Atoms.SpeciesAndCoordinates
1 Fe 5.732000 0.0000000 0.0000000 9.0 7.0
2 Co 7.165000 1.4330000 1.4330000 9.0 6.0
3 Fe 8.598000 0.0000000 0.0000000 9.0 7.0
4 Co 10.031000 1.4730000 1.4730000 9.0 6.0
5 Fe 11.464000 0.0000000 0.0000000 9.0 7.0
6 Co 12.897000 1.4730000 1.4730000 9.0 6.0
7 Fe 14.330000 0.0000000 0.0000000 9.0 7.0
8 O 16.490000 0.0000000 0.0000000 3.0 3.0
9 Mg 16.490000 1.4330000 1.4330000 4.0 4.0
10 O 18.516500 1.4330000 1.4330000 3.0 3.0
11 Mg 18.516500 0.0000000 0.0000000 4.0 4.0
12 O 20.543000 0.0000000 0.0000000 3.0 3.0
13 Mg 20.543000 1.4330000 1.4330000 4.0 4.0
14 O 22.569500 1.4330000 1.4330000 3.0 3.0
15 Mg 22.569500 0.0000000 0.0000000 4.0 4.0
16 O 24.596000 0.0000000 0.0000000 3.0 3.0
17 Mg 24.596000 1.4330000 1.4330000 4.0 4.0
18 Fe 26.756000 0.0000000 0.0000000 7.0 9.0
19 Co 28.189000 1.4330000 1.4330000 6.0 9.0
20 Ta 29.622000 0.0000000 0.0000000 6.5 6.5
21 Co 31.055000 1.4330000 1.4330000 6.0 9.0
22 Fe 32.488000 0.0000000 0.0000000 7.0 9.0
23 Co 33.921000 1.4330000 1.4330000 6.0 9.0
24 Fe 35.354000 0.0000000 0.0000000 7.0 9.0
25 Co 36.787000 1.4330000 1.4330000 6.0 9.0
Atoms.SpeciesAndCoordinates>

#
# Lead-Left
#

LeftLeadAtoms.Number 4
<LeftLeadAtoms.SpeciesAndCoordinates # Unit=Ang.
1 Fe 0.000000 0.0000000 0.0000000 9.0 7.0
2 Co 1.433000 1.4330000 1.4330000 9.0 6.0
3 Fe 2.866000 0.0000000 0.0000000 9.0 7.0
4 Co 4.299000 1.4330000 1.4330000 9.0 6.0
LeftLeadAtoms.SpeciesAndCoordinates>

#
# Lead-Right
#

RightLeadAtoms.Number 4
<RightLeadAtoms.SpeciesAndCoordinates # Unit=Ang.
1 Fe 38.220000 0.0000000 0.0000000 7.0 9.0
2 Co 39.653000 1.4330000 1.4330000 6.0 9.0
3 Fe 41.086000 0.0000000 0.0000000 7.0 9.0
4 Co 42.519000 1.4330000 1.4330000 6.0 9.0
RightLeadAtoms.SpeciesAndCoordinates>

#
# SCF or Electronic System
#

scf.XcType GGA-PBE # LDA|LSDA-CA|LSDA-PW|GGA-PBE
scf.SpinPolarization on # On|Off|NC
scf.ElectronicTemperature 1200.0 # default=300 (K)
scf.energycutoff 150.0 # default=150 (Ry)
scf.maxIter 500 # default=40
scf.EigenvalueSolver NEGF # DC|GDC|Cluster|Band
scf.lapack.dste dstevx # dstegr|dstedc|dstevx, default=dstegr
scf.Kgrid 2 6 6 # means n1 x n2 x n3
scf.Mixing.Type kerker # Simple|Rmm-Diis|Gr-Pulay|Kerker|Rmm-Diisk
scf.Init.Mixing.Weight 0.05 # default=0.30
scf.Min.Mixing.Weight 0.005 # default=0.001
scf.Max.Mixing.Weight 0.100 # default=0.40
scf.Kerker.factor 40.0 # default=1.0
scf.Mixing.History 60 # default=5
scf.Mixing.StartPulay 20 # default=6
scf.Mixing.EveryPulay 1 # default=6
scf.criterion 1.0e-1 # default=1.0e-6 (Hartree)
scf.restart off

#
# 1D FFT
#

1DFFT.NumGridK 900 # default=900
1DFFT.NumGridR 900 # default=900
1DFFT.EnergyCutoff 3600.0 # default=3DFFT.EnergyCutoff*3.0 (Ry)


===============================================================


How to solve this convergence problem??
It there better option? for example Pulay or Mixing parameter?

Thanks.

e
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