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Transport direction in 2D slab NEGF calculation
Date: 2018/09/28 15:58
Name: ZHOU Jiaqi   <jiaqi.zhou@buaa.edu.cn>

Dear all,

I have a problem on the transport direction in 2D slab NEGF calculation. In my lead input file I set a square unit cell to make the transport along a axis, as the following:

Atoms.UnitVectors.Unit Ang
<Atoms.UnitVectors
7.101262720 0.0000000000 0.0000000000
0.0000000000 2.4600000381 0.0000000000
0.0000000000 0.0000000000 1 3.3999996185
Atoms.UnitVectors>

However, in the NEGF calculation, the output file eUCellf is not a square any more, and the estdf file outputs the same. Namely, the original a axis has been changed, which can be confirmed by eciff output file. I wonder in this condition, whatfs the real transport direction?

Besides, this calculation got convergent after 8000 steps. I attach estdf, eUCellf and edatf file for reference.

Thank you very much for your help!

Yours Sincerely,
ZHOU Jiaqi


estdf file:

<Check_System> The system is slab.
lattice vectors (bohr)
A = 40.258725274487, 0.000000000000, 6.425067640238
B = 0.000000000000, 4.648726003903, 0.000000000000
C = 0.000000000000, 0.000000000000, 25.322327526027
reciprocal lattice vectors (bohr^-1)
RA = 0.156070150367, 0.000000000000, 0.000000000000
RB = -0.000000000000, 1.351592952974, 0.000000000000
RC = -0.039599885583, 0.000000000000, 0.248128269438


eUCellf file


Cell_Volume = 4739.118747914826 (Bohr^3)
GridVol = 0.016791095337 (Bohr^3)
Cell vectors (bohr) of the grid cell (gtv)
gtv_a = 0.251617032966, 0.000000000000, 0.040156672751
gtv_b = 0.000000000000, 0.258262555772, 0.000000000000
gtv_c = 0.000000000000, 0.000000000000, 0.258391097204
|gtv_a| = 0.254801274810
|gtv_b| = 0.258262555772
|gtv_c| = 0.258391097204


edatf file

#
# File Name
#

System.CurrrentDirectory ./ # default=./
System.Name bilayer
level.of.stdout 1 # default=1 (1-3)
level.of.fileout 1 # default=1 (0-2)
DATA.PATH ../DFT_DATA13

NEGF.filename.hks.l ../left-lead/left-lead.hks
NEGF.filename.hks.r ../right-lead/right-lead.hks

NEGF.SCF.Iter.Band 20
#NEGF.Num.Poles 100 # defalut=150
NEGF.scf.Kgrid 11 1 # defalut=1 1

#
# Transmission & Eigen Channel Analysis
#

NEGF.tran.Analysis on # default on
#NEGF.tran.energydiv 201 # default=200
NEGF.tran.energyrange -1 1 0.001 # default=-10.0 10.0 5.0e-3 (eV)
NEGF.tran.Kgrid 100 1 # default= 1 1

NEGF.tran.CurrentDensity off # default on

NEGF.tran.Channel off # default on

#
# Definition of Atomic Species
#

Species.Number 1
<Definition.of.Atomic.Species
C C7.0-s1p1 C_PBE13
Definition.of.Atomic.Species>


#
# Atoms
#

Atoms.SpeciesAndCoordinates.Unit Ang # Ang|AU


Atoms.Number 13
<Atoms.SpeciesAndCoordinates
1 C 7.101262720 0.000000000 0.000000000 2.0 2.0
2 C 7.811538259 1.230000019 3.3999996185 2.0 2.0
3 C 8.521600469 0.000000000 0.000000000 2.0 2.0
4 C 10.652000427 1.230000019 0.000000000 2.0 2.0
5 C 8.521600469 0.000000000 3.3999996185 2.0 2.0
6 C 10.652000427 1.230000019 3.3999996185 2.0 2.0
7 C 9.231662678 1.230000019 0.000000000 2.0 2.0
8 C 11.362063272 0.000000000 0.000000000 2.0 2.0
9 C 9.941938218 0.000000000 3.3999996185 2.0 2.0
10 C 12.072338176 1.230000019 3.3999996185 2.0 2.0
11 C 12.782401021 0.000000000 0.000000000 2.0 2.0
12 C 12.782401021 0.000000000 3.3999996185 2.0 2.0
13 C 13.492462595 1.230000019 0.000000000 2.0 2.0
Atoms.SpeciesAndCoordinates>

Atoms.UnitVectors.Unit Ang # Ang|AU

#<Atoms.UnitVectors
# 8.521600469 0.0000000000 0.0000000000
# 0.0000000000 2.4600000381 0.0000000000
# 0.0000000000 0.0000000000 13.3999996185
#Atoms.UnitVectors>


#
# Lead-Left
#

LeftLeadAtoms.Number 7
<LeftLeadAtoms.SpeciesAndCoordinates # Unit=Ang.
1 C 0.000000000 0.000000000 0.000000000 2.0 2.0
2 C 2.130400117 1.230000019 0.000000000 2.0 2.0
3 C 0.710062368 1.230000019 0.000000000 2.0 2.0
4 C 2.840462486 0.000000000 0.000000000 2.0 2.0
5 C 4.260800234 0.000000000 0.000000000 2.0 2.0
6 C 6.391200510 1.230000019 0.000000000 2.0 2.0
7 C 4.970862444 1.230000019 0.000000000 2.0 2.0
LeftLeadAtoms.SpeciesAndCoordinates>


#
# Lead-Right
#


RightLeadAtoms.Number 7

<RightLeadAtoms.SpeciesAndCoordinates # Unit=Ang.
1 C 14.202738769 1.230000019 3.3999996185 2.0 2.0
2 C 14.912801137 0.000000000 3.3999996185 2.0 2.0
3 C 16.333138886 1.230000019 3.3999996185 2.0 2.0
4 C 17.043201255 0.000000000 3.3999996185 2.0 2.0
5 C 18.463539003 1.230000019 3.3999996185 2.0 2.0
6 C 19.173601213 0.000000000 3.3999996185 2.0 2.0
7 C 20.593939279 1.230000019 3.3999996185 2.0 2.0
RightLeadAtoms.SpeciesAndCoordinates>


#
# SCF or Electronic System
#


scf.XcType GGA-PBE # LDA|LSDA-CA|LSDA-PW|GGA-PBE
scf.SpinPolarization off # On|Off|NC
scf.ElectronicTemperature 300.0 # default=300 (K)
#scf.energycutoff 200.0 # default=150 (Ry)
#scf.Ngrid 140 140 100 # about=200 (Ry)
scf.maxIter 10000 # default=40
scf.EigenvalueSolver NEGF # DC|GDC|Cluster|Band
scf.lapack.dste dstevx # dstegr|dstedc|dstevx, default=dstegr
scf.Kgrid 1 11 1 # means n1 x n2 x n3
scf.Mixing.Type Kerker # Simple|Rmm-Diis|Gr-Pulay|Kerker|Rmm-Diisk
scf.Kerker.factor 20.0 # default=1
scf.Init.Mixing.Weight 0.05 # default=0.30
scf.Min.Mixing.Weight 0.005 # default=0.001
scf.Max.Mixing.Weight 0.2 # 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-7 # default=1.0e-6 (Hartree)


#
# MD or Geometry Optimization
#

MD.Type Nomd # Opt|EF|BFGS|RF|DIIS
MD.Opt.DIIS.History 10 # default=3
MD.Opt.StartDIIS 6 # default=5
MD.Opt.EveryDIIS 5 # default=10
MD.maxIter 200 #
MD.Opt.criterion 1.0e-4 # default=1.0e-4 (a.u.)

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