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Questions about the magnetic moment in NEGF calculations
Date: 2019/07/17 21:46
Name: H Y ZHOU

Dear all,

I'm trying to calculate TMR of the Fe/MgO/Fe system. However, the magnetic moments of Fe atoms always seem strange. The magnetic moments of interfacial Fe atoms, which are about 1.29ƒĘB, are much lower than usual ones. However, I don't know why this phenomenon occurs and if I should change some parameters, such as NEGF.Num.Poles, scf.ElectronicTemperature or scf.energycutoff.

Looking forward to your reply. Thank you very much in advance.

Best,
H Y


Following is part of the .md file which is the NEGF calculation result.
time= 0.000 (fs) Energy= -1387.17333 (Hartree) Cell_Vectors= 27.70100 0.00000 0.00000 0.00000 2.83000 0.00000 0.00000 0.00000 2.83000

atom x y z magnetic moment
Fe 0.00000 1.41500 1.41500 2.22110
Fe 1.41600 0.00000 0.00000 2.22688
Fe 2.83200 1.41500 1.41500 2.12162
Fe 4.24800 0.00000 0.00000 1.29266
O 6.48100 0.00000 0.00000 0.00698
O 8.70150 1.41500 1.41500 0.00018
O 10.92200 0.00000 0.00000 -0.00004
O 13.14250 1.41500 1.41500 -0.00000
O 15.36300 0.00000 0.00000 -0.00004
O 17.58350 1.41500 1.41500 0.00018
O 19.80400 0.00000 0.00000 0.00699
Mg 6.48100 1.41500 1.41500 -0.04765
Mg 8.70150 0.00000 0.00000 0.00224
Mg 10.92200 1.41500 1.41500 0.00005
Mg 13.14250 0.00000 0.00000 0.00002
Mg 15.36300 1.41500 1.41500 0.00005
Mg 17.58350 0.00000 0.00000 0.00224
Mg 19.80400 1.41500 1.41500 -0.04765
Fe 22.03700 0.00000 0.00000 1.29263
Fe 23.45300 1.41500 1.41500 2.12160
Fe 24.86900 0.00000 0.00000 2.22688
Fe 26.28500 1.41500 1.41500 2.22110



Here is my input file.

NEGF.Num.Poles 200 # default=150
NEGF.scf.Kgrid 7 7 # default=1 1

NEGF.scf.Iter.Band 10 # defalut=6 No idea about what's this
NEGF.Output.for.TranMain off # on

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)

NEGF.tran.CurrentDensity off
NEGF.tran.Channel off

NEGF.tran.energydiv 201 # default=200
NEGF.tran.energyrange -5 5 1e-3 # default=-10.0 10.0 1.0e-3 (eV)
NEGF.tran.Kgrid 120 120 # default= 1 1

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 7 7 # default=1 1



#
# Definition of Atomic Species
#

Species.Number 3
<Definition.of.Atomic.Species
Fe Fe5.0H-s2p2d1 Fe_PBE13H
Mg Mg7.0-s2p2 Mg_PBE13
O O5.0-s2p2d1 O_PBE13
Definition.of.Atomic.Species>


#
# Atoms
#

Atoms.SpeciesAndCoordinates.Unit Ang # Ang|AU
Atoms.Number 14
<Atoms.SpeciesAndCoordinates
1 O 6.481 0.000 0.000 3.0 3.0
2 O 8.7015 1.415 1.415 3.0 3.0
3 O 10.9220 0.000 0.000 3.0 3.0
4 O 13.1425 1.415 1.415 3.0 3.0
5 O 15.3630 0.000 0.000 3.0 3.0
6 O 17.5835 1.415 1.415 3.0 3.0
7 O 19.8040 0.000 0.000 3.0 3.0
8 Mg 6.481 1.415 1.415 4.0 4.0
9 Mg 8.7015 0.000 0.000 4.0 4.0
10 Mg 10.9220 1.415 1.415 4.0 4.0
11 Mg 13.1425 0.000 0.000 4.0 4.0
12 Mg 15.3630 1.415 1.415 4.0 4.0
13 Mg 17.5835 0.000 0.000 4.0 4.0
14 Mg 19.8040 1.415 1.415 4.0 4.0
Atoms.SpeciesAndCoordinates>

#
# Lead-Left
#

LeftLeadAtoms.Number 4
<LeftLeadAtoms.SpeciesAndCoordinates # Unit=Ang.
1 Fe 0.000 1.415 1.415 9.0 7.0
2 Fe 1.416 0.000 0.000 9.0 7.0
3 Fe 2.832 1.415 1.415 9.0 7.0
4 Fe 4.248 0.000 0.000 9.0 7.0
LeftLeadAtoms.SpeciesAndCoordinates>

#
# Lead-Right
#
RightLeadAtoms.Number 4
<RightLeadAtoms.SpeciesAndCoordinates # Unit=Ang.
1 Fe 22.0370 0.000 0.000 9.0 7.0
2 Fe 23.4530 1.415 1.415 9.0 7.0
3 Fe 24.8690 0.000 0.000 9.0 7.0
4 Fe 26.2850 1.415 1.415 9.0 7.0
RightLeadAtoms.SpeciesAndCoordinates>

#
# SCF or Electronic System
#

scf.XcType GGA-PBE # LDA|LSDA-CA|LSDA-PW|GGA-PBE
scf.SpinPolarization On # On|Off|NC
scf.SpinOrbit.Coupling Off # On|Off, default=off
scf.ElectronicTemperature 300.0 # default=300 (K)
scf.energycutoff 220.0 # default=150 (Ry)
scf.maxIter 5000 # default=40
scf.EigenvalueSolver NEGF # DC|GDC|Cluster|Band
#scf.lapack.dste dstevx # dstegr|dstedc|dstevx, default=dstegr
scf.Kgrid 1 7 7 # means n1 x n2 x n3
scf.Mixing.Type rmm-diisk # Simple|Rmm-Diis|Gr-Pulay|Kerker|Rmm-Diisk
scf.Kerker.factor 20.0 # default=1
scf.Init.Mixing.Weight 0.01 # default=0.30
scf.Min.Mixing.Weight 0.001 # default=0.001
scf.Max.Mixing.Weight 0.01 # default=0.40
scf.Mixing.History 20 # default=5
scf.Mixing.StartPulay 20 # default=6
scf.Mixing.EveryPulay 1 # default=6
scf.criterion 1.0e-6 # default=1.0e-6 (Hartree)


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