Siesta

error real space spin density difference of Right electrode after ts calculation at 0 bias

Asked by 翟明星 on 2020-11-21

Dear all:

 I calculate the transport property of graphyne nanoribbons at antiparallel spin configuration. Analysis of "Rho.grid.nc" of the Scattering Region, I found real space spin density difference of the Right electrode is totally different form that of the right electrode bulk . I don't know the reason. Can someone give me some advice? My fdf file of the SR as follow:

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
SystemName z4 # Descriptive name of the system
SystemLabel z4 # Short name for naming files

# Output options

#WriteCoorStep 1
WriteMullikenPop 1
WriteDenchar T # Write information for DENCHAR

# Species and atoms

NumberOfSpecies 2
NumberOfAtoms 288

%block ChemicalSpeciesLabel
  1 6 C
  2 1 H
%endblock ChemicalSpeciesLabel

%block kgrid_Monkhorst_Pack
   1 0 0 0.0
   0 1 0 0.0
   0 0 6 0.0
%endblock Kgrid_Monkhorst_Pack

LatticeConstant 1.0 Ang

%block LatticeVectors
58.399550000000000 0.000000000000000 0.000000000
 0.000000000000000 30.000000000000000 0.000000000
 0.000000000000000 0.0000000000000000 62.83239471
%endblock LatticeVectors

#%block AtomicCoordinatesOrigin
#0.0 0.0 -13.9627543800
#%block AtomicCoordinatesOrigin

xc.functional LDA # Exchange-correlation functional
xc.authors CA # Exchange-correlation version

SpinPolarized T # Logical parameters are: yes or no
MeshCutoff 300. Ry # Mesh cutoff. real space mesh

# SCF options
MaxSCFIterations 60 # Maximum number of SCF iter
DM.MixingWeight 0.1 # New DM amount for next SCF cycle
DM.Tolerance 1.d-4 # Tolerance in maximum difference
DM.UseSaveDM T # to use continuation files
DM.NumberPulay 6

ElectronicTemperature 25 meV

# AtomionicTemperature.rdinates
AtomicCoordinatesFormat Ang
%block AtomicCoordinatesAndAtomicSpecies
16.10000000 15.00000000 1.74534000 1 1
16.10000000 15.00000000 8.72671719 1 2
16.79975000 15.00000000 2.95735000 1 3
16.79975000 15.00000000 9.93872719 1 4
..........
34.93790000 15.00000000 62.29905752 1 286
15.00000000 15.00000000 50.61498033 2 287
15.00000000 15.00000000 57.59635752 2 288
%endblock AtomicCoordinatesAndAtomicSpecies

#############################################################
####transiesta
SolutionMethod transiesta
%include NEW.fdf
TS.SaveHS true

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

NEW.fdf
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
TS.Voltage 0.00000 eV
TS.ElectronicTemperature 25 meV
%block TS.ChemPots
  Left
  Right
%endblock TS.ChemPots

%block TS.ChemPot.Left
  mu V/2
  contour.eq
    begin
      c-Left
      t-Left
    end
%endblock TS.ChemPot.Left
%block TS.ChemPot.Right
  mu -V/2
  contour.eq
    begin
      c-Right
      t-Right
    end
%endblock TS.ChemPot.Right

TS.Elecs.Bulk true
TS.Elecs.DM.Update cross-terms
TS.Elecs.GF.ReUse true
%block TS.Elecs
  Left
  Right
%endblock TS.Elecs

%block TS.Elec.Left
  HS ../../../lead1/z4.TSHS
  chem-pot Left
  semi-inf-dir -a3
  elec-pos begin 1
  used-atoms 64
%endblock TS.Elec.Left

%block TS.Elec.Right
  HS ../../../lead2/z4.TSHS
  chem-pot Right
  semi-inf-dir +a3
  elec-pos end -1
  used-atoms 64
%endblock TS.Elec.Right

TS.Contours.Eq.Pole 2.50000 eV
%block TS.Contour.c-Left
  part circle
   from -40.00000 eV + V/2 to -10. kT + V/2
    points 40
     method g-legendre
%endblock TS.Contour.c-Left
%block TS.Contour.t-Left
  part tail
   from prev to inf
    points 10
     method g-fermi
%endblock TS.Contour.t-Left
%block TS.Contour.c-Right
  part circle
   from -40.00000 eV - V/2 to -10. kT - V/2
    points 40
     method g-legendre
%endblock TS.Contour.c-Right
%block TS.Contour.t-Right
  part tail
   from prev to inf
    points 10
     method g-fermi
%endblock TS.Contour.t-Right

TS.Elecs.Eta 0.0001000000 eV
%block TS.Contours.nEq
  neq
%endblock TS.Contours.nEq
%block TS.Contour.nEq.neq
  part line
   from -|V|/2 - 5 kT to |V|/2 + 5 kT
    delta 0.01 eV
     method mid-rule
%endblock TS.Contour.nEq.neq

# TBtrans options

TBT.Elecs.Eta 0.0001000000 eV

%block TBT.Contours
  neq
%endblock TBT.Contours

%block TBT.Contour.neq
  part line
   from -2.00000 eV to 2.00000 eV
    delta 0.01000 eV
     method mid-rule
%endblock TBT.Contour.neq
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

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翟明星
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Nick Papior (nickpapior) said : #1

Are you sure the systems converged correctly? And that the TS cycle retained charges?

翟明星 (mxzhai) said : #2

The TS cycle in outfile as follow:
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
         iscf Eharris(eV) E_KS(eV) FreeEng(eV) dDmax Ef(eV) dHmax(eV)
ts-scf: 1 -41864.557886 -41864.549465 -41864.549465 0.000158 -4.496750 0.004871
     spin moment: S , {S} = 0.87055 0.0 0.0 0.87055
timer: Routine,Calls,Time,% = TS 1 9.582 27.68
ts-q: D E1 C1 E2 C2 dQ dQtot
ts-q: 301.193 118.617 3.668 118.617 3.647 4.258E-1
ts-q: 301.435 118.024 3.691 118.024 3.701 -4.512E-1 -2.537E-2
ts-Vha: 0.14379E-01 eV
ts-scf: 2 -41864.031327 -41864.291083 -41864.291083 0.001881 -4.496750 0.131296
     spin moment: S , {S} = 0.87699 0.0 0.0 0.87699
ts-q: D E1 C1 E2 C2 dQ dQtot
ts-q: 301.200 118.617 3.667 118.617 3.650 4.354E-1
ts-q: 301.448 118.024 3.690 118.024 3.703 -4.361E-1 -6.489E-4
ts-Vha: 0.11872E-01 eV
ts-scf: 3 -41864.791319 -41864.541493 -41864.541493 0.001804 -4.496750 0.000957
     spin moment: S , {S} = 0.87146 0.0 0.0 0.87146
ts-q: D E1 C1 E2 C2 dQ dQtot
ts-q: 301.200 118.617 3.667 118.617 3.650 4.356E-1
ts-q: 301.448 118.024 3.690 118.024 3.703 -4.362E-1 -6.326E-4
ts-Vha: 0.11861E-01 eV
ts-scf: 4 -41864.540831 -41864.541162 -41864.541162 0.000009 -4.496750 0.000847
     spin moment: S , {S} = 0.87175 0.0 0.0 0.87175
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

By comparing the reference, the transmission is right. And the spin magnetic moment of atoms in device region is right.

Nick Papior (nickpapior) said : #3

That looks fine.

How did you compare the charge?

翟明星 (mxzhai) said : #4

I calculate the Mulliken population and Rho. I'm just making a rough comparison. In the device region, spin density at every atom around is right. But the spin polarization direction of right electrode part in ts calculation is opposite direction of the bulk right electrode. And spin density of the interface between electrode and SR is a little mix. So I think that maybe some setup is incorrect in my calculation. I tried some parameter such as: TS.poission and TS.ChargeCorrection, but nothing has changed. Now I have no idea about this. Can you give me some advice?

Nick Papior (nickpapior) said : #5

Do you have different initial spin configurations in your leads?

Because that may be a bit difficult to enforce in TS calculations.

If you want to ensure that the charge-density and electrode density is consistent with the electrodes you should ensure that the *TSDE files for the electrodes are also present.

Then add this

TS.Elecs.DM.Init bulk

This will copy in the electrode density matrix directly into the electrode blocks. But please note that this will probably disrupt the SCF cycles and forces you to really be careful in your calculations.

You may aid SCF by having some buffer atoms where the spin is slowly rotating so that they match both electrodes (also not easy).

翟明星 (mxzhai) said : #6

Yes. magnetization direction of Left lead is spin up, and that of right lead is spin down.
Thank you! I will try.
I have another question. Is my previous charge density in ts calculation correct?

Nick Papior (nickpapior) said : #7

What do you mean?

I would say if you don't have the same spin-configuration in the leads you will have some trustworthy problems... :(

翟明星 (mxzhai) said : #8

Ok. Thanks a lot.