Dear All，
I met some problems when I calculated transport current. I wonder if you can help me with the following questions. Thank you very much.
(1) My system is a vertical heterostructure of borophene and graphene. I need to calculate the current of this system with only about 4e-12 A. When the borophene layer is taken out, the graphene transport is normal and the current can reach to 2e-6 A. When the graphene layer is removed, the transport current of the borophene layer is still very small, only about 2e-14 A. I think it's a strange phenomenon since the borophene is metallic. When I lengthen the distance between borophene and graphene (about 13 angstrom), the interaction between graphene and borophene can be neglected and borophene and graphene have independent transport properties. However, the total current is much smaller than that of graphene monolayer, about 2e-13A.
(2) I tried to change the number of k points in tbtrans calcultion, but I found that the current is very sensitive to this change. The convergent current value can not be reached no matter how many k points are increased.
(3) the transmission spectrum and DOS spectrum have some peaks at some energy values, how to make the results smoother so as to have no effect the analysis of transport characteristics.
I met some problems when I calculated transport current. I wonder if you can help me with the following questions. Thank you very much.
(1) My system is a vertical heterostructure of borophene and graphene. I need to calculate the current of this system with only about 4e-12 A. When the borophene layer is taken out, the graphene transport is normal and the current can reach to 2e-6 A. When the graphene layer is removed, the transport current of the borophene layer is still very small, only about 2e-14 A. I think it's a strange phenomenon since the borophene is metallic. When I lengthen the distance between borophene and graphene (about 13 angstrom), the interaction between graphene and borophene can be neglected and borophene and graphene have independent transport properties. However, the total current is much smaller than that of graphene monolayer, about 2e-13A.
(2) I tried to change the number of k points in tbtrans calcultion, but I found that the current is very sensitive to this change. The convergent current value can not be reached no matter how many k points are increased.
(3) the transmission spectrum and DOS spectrum have some peaks at some energy values, how to make the results smoother so as to have no effect the analysis of transport characteristics.
Here is one of my input files:
SolutionMethod Transiesta
SystemName bor-gra
SystemLabel bor-gra
SystemLabel bor-gra
NumberOfSpecies 1
%block ChemicalSpeciesLabel
1 5 B
%endblock ChemicalSpeciesLabel
K-points
%block kgrid_Monkhorst_Pack
21 0 0 0.0
0 1 0 0.0
0 0 100 0.0
%endblock kgrid_Monkhorst_Pack
%block kgrid_Monkhorst_Pack
21 0 0 0.0
0 1 0 0.0
0 0 100 0.0
%endblock kgrid_Monkhorst_Pack
NumberOfAtoms 75
LatticeConstant 1.0 Ang
%block LatticeVectors
8.646867 0.00000 0.00000
0.00000 20.00000 0.00000
0.00000 0.00000 24.907988
%endblock LatticeVectors
%block LatticeVectors
8.646867 0.00000 0.00000
0.00000 20.00000 0.00000
0.00000 0.00000 24.907988
%endblock LatticeVectors
AtomicCoordinatesFormat Ang
%block AtomicCoordinatesAndAtomicSpecies
2.856259 0.363248 0.000000 1
5.733159 0.393111 0.000000 1
8.610725 0.360136 0.000000 1
4.294464 0.395949 0.866486 1
7.171205 0.394481 0.866504 1
1.417779 0.352945 0.866940 1
5.732602 0.414308 1.681051 1
2.856264 0.370402 1.681524 1
8.609220 0.364605 1.681534 1
8.609220 0.364605 3.297428 1
2.856264 0.370402 3.297439 1
5.732602 0.414308 3.297912 1
1.417779 0.352945 4.112023 1
7.171205 0.394481 4.112458 1
4.294464 0.395949 4.112476 1
2.856259 0.363248 4.978962 1
5.733159 0.393111 4.978962 1
8.610725 0.360136 4.978962 1
4.294464 0.395949 5.845448 1
7.171205 0.394481 5.845466 1
1.417779 0.352945 5.845902 1
5.732602 0.414308 6.660013 1
2.856264 0.370402 6.660486 1
8.609220 0.364605 6.660496 1
8.609220 0.364605 8.276391 1
2.856264 0.370402 8.276401 1
5.732602 0.414308 8.276874 1
1.417779 0.352945 9.090985 1
7.171205 0.394481 9.091421 1
4.294464 0.395949 9.091439 1
2.856259 0.363248 9.957925 1
5.733159 0.393111 9.957925 1
8.610725 0.360136 9.957925 1
4.294464 0.395949 10.824411 1
7.171205 0.394481 10.824429 1
1.417779 0.352945 10.824865 1
5.732602 0.414308 11.638976 1
2.856264 0.370402 11.639449 1
8.609220 0.364605 11.639459 1
8.609220 0.364605 13.255353 1
2.856264 0.370402 13.255364 1
5.732602 0.414308 13.255836 1
1.417779 0.352945 14.069948 1
7.171205 0.394481 14.070383 1
4.294464 0.395949 14.070401 1
2.856259 0.363248 14.936887 1
5.733159 0.393111 14.936887 1
8.610725 0.360136 14.936887 1
4.294464 0.395949 15.803373 1
7.171205 0.394481 15.803391 1
1.417779 0.352945 15.803827 1
5.732602 0.414308 16.617938 1
2.856264 0.370402 16.618411 1
8.609220 0.364605 16.618421 1
8.609220 0.364605 18.234315 1
2.856264 0.370402 18.234326 1
5.732602 0.414308 18.234799 1
1.417779 0.352945 19.048910 1
7.171205 0.394481 19.049345 1
4.294464 0.395949 19.049364 1
2.856259 0.363248 19.915850 1
5.733159 0.393111 19.915850 1
8.610725 0.360136 19.915850 1
4.294464 0.395949 20.782336 1
7.171205 0.394481 20.782354 1
1.417779 0.352945 20.782789 1
5.732602 0.414308 21.596900 1
2.856264 0.370402 21.597373 1
8.609220 0.364605 21.597384 1
8.609220 0.364605 23.213278 1
2.856264 0.370402 23.213289 1
5.732602 0.414308 23.213761 1
1.417779 0.352945 24.027873 1
7.171205 0.394481 24.028308 1
4.294464 0.395949 24.028326 1
%endblock AtomicCoordinatesAndAtomicSpecies
%block AtomicCoordinatesAndAtomicSpecies
2.856259 0.363248 0.000000 1
5.733159 0.393111 0.000000 1
8.610725 0.360136 0.000000 1
4.294464 0.395949 0.866486 1
7.171205 0.394481 0.866504 1
1.417779 0.352945 0.866940 1
5.732602 0.414308 1.681051 1
2.856264 0.370402 1.681524 1
8.609220 0.364605 1.681534 1
8.609220 0.364605 3.297428 1
2.856264 0.370402 3.297439 1
5.732602 0.414308 3.297912 1
1.417779 0.352945 4.112023 1
7.171205 0.394481 4.112458 1
4.294464 0.395949 4.112476 1
2.856259 0.363248 4.978962 1
5.733159 0.393111 4.978962 1
8.610725 0.360136 4.978962 1
4.294464 0.395949 5.845448 1
7.171205 0.394481 5.845466 1
1.417779 0.352945 5.845902 1
5.732602 0.414308 6.660013 1
2.856264 0.370402 6.660486 1
8.609220 0.364605 6.660496 1
8.609220 0.364605 8.276391 1
2.856264 0.370402 8.276401 1
5.732602 0.414308 8.276874 1
1.417779 0.352945 9.090985 1
7.171205 0.394481 9.091421 1
4.294464 0.395949 9.091439 1
2.856259 0.363248 9.957925 1
5.733159 0.393111 9.957925 1
8.610725 0.360136 9.957925 1
4.294464 0.395949 10.824411 1
7.171205 0.394481 10.824429 1
1.417779 0.352945 10.824865 1
5.732602 0.414308 11.638976 1
2.856264 0.370402 11.639449 1
8.609220 0.364605 11.639459 1
8.609220 0.364605 13.255353 1
2.856264 0.370402 13.255364 1
5.732602 0.414308 13.255836 1
1.417779 0.352945 14.069948 1
7.171205 0.394481 14.070383 1
4.294464 0.395949 14.070401 1
2.856259 0.363248 14.936887 1
5.733159 0.393111 14.936887 1
8.610725 0.360136 14.936887 1
4.294464 0.395949 15.803373 1
7.171205 0.394481 15.803391 1
1.417779 0.352945 15.803827 1
5.732602 0.414308 16.617938 1
2.856264 0.370402 16.618411 1
8.609220 0.364605 16.618421 1
8.609220 0.364605 18.234315 1
2.856264 0.370402 18.234326 1
5.732602 0.414308 18.234799 1
1.417779 0.352945 19.048910 1
7.171205 0.394481 19.049345 1
4.294464 0.395949 19.049364 1
2.856259 0.363248 19.915850 1
5.733159 0.393111 19.915850 1
8.610725 0.360136 19.915850 1
4.294464 0.395949 20.782336 1
7.171205 0.394481 20.782354 1
1.417779 0.352945 20.782789 1
5.732602 0.414308 21.596900 1
2.856264 0.370402 21.597373 1
8.609220 0.364605 21.597384 1
8.609220 0.364605 23.213278 1
2.856264 0.370402 23.213289 1
5.732602 0.414308 23.213761 1
1.417779 0.352945 24.027873 1
7.171205 0.394481 24.028308 1
4.294464 0.395949 24.028326 1
%endblock AtomicCoordinatesAndAtomicSpecies
PAO.BasisType split
PAO.BasisSize SZP
PAO.EnergyShift 275 meV
PAO.SplitNorm 0.15
TS.SolutionMethod btd
TS.SCF.Initialize diagon
#TS.Analyze .true.
TS.BTD.Optimize speed
TS.Poisson ramp-central
TS.Hartree.Fix plane
TS.SCF.Initialize diagon
#TS.Analyze .true.
TS.BTD.Optimize speed
TS.Poisson ramp-central
TS.Hartree.Fix plane
SCF.DM.Converge .true.
SCF.DM.Tolerance 1e-4
SCF.DM.Tolerance 1e-4
MeshCutoff 250. Ry
XC.functional GGA
XC.authors PBE
SolutionMethod transiesta
XC.functional GGA
XC.authors PBE
SolutionMethod transiesta
ElectronicTemperature 300 K
OccupationFunction FD
OccupationFunction FD
MaxSCFIterations 200
DM.MixingWeight 0.1
DM.Tolerance 0.001
DM.NumberPulay 6
DM.UseSaveDM .true.
DM.MixSCF1 .true.
DM.MixingWeight 0.1
DM.Tolerance 0.001
DM.NumberPulay 6
DM.UseSaveDM .true.
DM.MixSCF1 .true.
MD.NumCGSteps 0
WriteMullikenPop 1
WriteForces T
SaveHS T
WriteForces T
SaveHS T
TS.Voltage 0.00000 eV
TS.Elecs.Neglect.Principal .true.
%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 ./left.TSHS
chem-pot Left
semi-inf-dir -a3
elec-pos begin 1
# used-atoms 24
%endblock TS.Elec.Left
%block TS.Elec.Right
HS ./left.TSHS
chem-pot Right
semi-inf-dir +a3
elec-pos end -1
# used-atoms 24
%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 25
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 25
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.T.Eig 9
TBT.Elecs.Eta 0.0001000000 eV
TBT.Voltage 0.50000 eV
%block TBT.Contours
neq
%endblock TBT.Contours
%block TBT.Contour.neq
part line
from -5.00000 eV to 5.00000 eV
delta 0.01 eV
method mid-rule
%endblock TBT.Contour.neq
%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 ./left.TSHS
chem-pot Left
semi-inf-dir -a3
elec-pos begin 1
# used-atoms 24
%endblock TS.Elec.Left
%block TS.Elec.Right
HS ./left.TSHS
chem-pot Right
semi-inf-dir +a3
elec-pos end -1
# used-atoms 24
%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 25
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 25
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.T.Eig 9
TBT.Elecs.Eta 0.0001000000 eV
TBT.Voltage 0.50000 eV
%block TBT.Contours
neq
%endblock TBT.Contours
%block TBT.Contour.neq
part line
from -5.00000 eV to 5.00000 eV
delta 0.01 eV
method mid-rule
%endblock TBT.Contour.neq
TS.BTD.Pivot atom+rev-PCG+Left
TBT.DOS.A .true.
#TBT.Spin all
TBT.DOS.A .true.
#TBT.Spin all
%block TBT.k
350 0 0 0.
0 1 0 0.
0 0 1 0.
%endblock
350 0 0 0.
0 1 0 0.
0 0 1 0.
%endblock
best regards，
zhy
-- SIESTA is supported by the Spanish Research Agency (AEI) and by the European H2020 MaX Centre of Excellence (http://www.max-centre.eu/)
