Dear Jose A. Torres:
Thank you very for your reply.
From your explanations, I know that, for the special voltage, the current
will converge to the dense k-mesh and larger TSTBT.NPoints. Is it right?
My example system is a tunneling junction with a insulated slab layer
sandwiched two different electrode of Pt and SrRuO3. I do not know if is it
right for my sturcture? Please give me some suggestion for the fdf file and
the calculated flow. My calculated flows are followed:
1 Firstly, considering the relaxation of electrode atoms (Pt and SrRuO3) and
insulated barrier atom in the interface, I include several SrRuO3 (leftt) and
Pt (right) layers with insulated layer as a whole, and optimize the whole
structure.
2 I make the whole optimized structure for a scattering region. Then I add two
unit cells SrRuO3 on the left side with one unit cell for the left buttfer
layer and two unit cells Pt on the right side one unit cell for the left
buttfer layer.
Moreover, because our system is different for the left and right electrode, the
fermi energy for the for the left and right electrode should be different.
However, I find that the followed hint for the Transiesta calculation with the
same Efermi for the left and right electrode. I do not the right reason.
I want to get your help once again.
" Begin LEFT
unit cell:
7.3072 0.0000 0.0000
0.0000 7.3072 0.0000
0.0000 0.0000 7.3072
Size: 1600
Left.GF already exist, will be overwritten!
Efermi: 3.674899422453221E-002
GF: Spin number -> 1
Got LEFT Electrode GF
Done
Begin RIGHT
unit cell:
7.3072 0.0000 0.0000
0.0000 7.3072 0.0000
0.0000 0.0000 7.5336
Size: 1296
Right.GF & nbsp; already exist, will be overwritten!
Efermi: -3.674899422453221E-002
GF: Spin number -> 1
Got RIGHT Electrode GF
"
The fdf file:
SystemName 2BTO
SystemLabel 2BTO
==================================================
==================================================
# SPECIES AND BASIS
# Number of species
NumberOfSpecies 6
%block ChemicalSpeciesLabel
1 8 O
2 22 Ti
3 38 Sr
4 44 Ru
5 56 Ba
6 78 Pt
%endblock ChemicalSpeciesLabel
PAO.BasisSize SZP
PAO.EnergyShift 0.005 Ry
==================================================
==================================================
# K-points
%block kgrid_Monkhorst_Pack
6 0 0 0.0
0 6 0 0.0
0 0 50 0.5
%endblock kgrid_Monkhorst_Pack
==================================================
# UNIT CELL
LatticeConstant 1.0 Ang
%block LatticeVectors
3.86 6800000 0.00000000000 0.0000000000
0.000000000 3.86680000000 0.0000000000
0.000000000 0.00000000000 47.838600000
%endblock LatticeVectors
# Atomic coordinates
NumberOfAtoms 56
AtomicCoordinatesFormat Fractional
%block AtomicCoordinatesAndAtomicSpecies
0 0.5 0 1
0.5 0 0 1
0.5 0.5 0 4
0.5 0.5 0.040415 1
0 0 0.040415 3
0.5 0 0.08083 1
0 0.5 0.08083 1
0.5 0.5 0.08083 4
0.5 0.5 0.121245 1
0 0 0.121245 3
0.5 0 0.16166 1
0 0.5 0.16166 1
0.5 0.5 0.165386 4
0.5 0.5 0.206666 1
0 0 0.209419 3
0.5 0 0.247371 &nbs p; 1
0 0.5 0.247371 1
0.5 0.5 0.248572 4
0.5 0.5 0.289628 1
0 0 0.290013 3
0.5 0.5 0.330969 4
0.5 0 0.331453 1
0 0.5 0.331453 1
0 0 0.370665 &nb sp; 3
0.5 0.5 0.372155 1
0.5 0.5 0.410913 2
0.5 0 0.411981 1
0 0.5 0.411981 1
0 0 0.453803 5
0.5 0.5 0.455417 1
0.5 0.5 0.49534 2
0.5 0 0.497249 1
0 0.5 0.497 249 1
0 0 0.538662 5
0.5 0.5 0.540272 1
0.5 0.5 0.580389 2
0.5 0 0.580785 1
0 0.5 0.580785 1
0.5 0 0.625007 6
0 0.5 0.625007 6
0.5 0.5 0.666959 6
0 0 0.66737 6
0.5 0 0.708495 6
0 0.5 0.708495 6
0.5 0.5 0.749674 6
0 0 0.749529 6
0.5 0 0.791664 6
0 0.5 0.791664 6
0 0 0.833331 6
0.5 &nb sp; 0.5 0.833331 6
0.5 0 0.874998 6
0 0.5 0.874998 6
0 0 0.916666 6
0.5 0.5 0.916666 6
0.5 0 0.958333 6
0 0.5 0.958333 6
%endblock AtomicCoordinatesAndAtomicSpecies
==================================================
==================================================
# Genera l variables
ElectronicTemperature 300 K
MeshCutoff 350. Ry
xc.functional LDA # Exchange-correlation functional
xc.authors CA
SpinPolarized .false.
SolutionMethod Transiesta
==================================================
==================================================
# SCF variables
DM.MixSCF1 T
MaxSCFIterations 800 # Maximum number of SCF iter
DM.MixingWeight 0.03 # New DM amount for next SCF cycle
DM.Tolerance 1.d-4 # Tolerance in maximum difference
DM.UseSaveDM true # to use continuation files
DM.NumberPulay 8
#DM.NumberKick 20
#Kgrid_cutoff 30 Bohr
Diag.DivideAndConquer no
TS.MixH true
==================================================
==================================================
# MD variables
MD.FinalTimeStep 1
MD.TypeOfRun CG
MD.NumCGsteps 000
MD.UseSaveXV .true.
==================================================
==================================================
# Output va riables
WriteMullikenPop 1
WriteBands .false.
SaveRho .false.
SaveDeltaRho .false.
SaveHS .false.
SaveElectrostaticPotential True
SaveTotalPotential no
WriteCoorXmol &n bsp; .true.
WriteMDXmol .true.
WriteMDhistory .false.
WriteEigenvalues yes
==================================================
==================================================
# Parallel variables
Diag.ParallelOverK yes
==================================================
==================================================
# Transiesta information
# GF OPTIONS
TS.ComplexContour.Emin -30.0 eV
TS.ComplexContour.NPoles 03
TS.ComplexContour.NCircle 30
TS.ComplexContour.NLine &nb sp; 10
# BIAS OPTIONS
TS.biasContour.NumPoints 15
TS.UpdateDMCROnly false
# TS OPTIONS
TS.Voltage -1.000000 eV
# TBT OPTIONS
TS.TBT.Emin -1.0 eV
TS.TBT.Em 1.0 eV
TS.TBT.NPoints 800
TS.mixH true
TS.TBT.NEigen 3
TS.TBT.Eta 0.000001 Ry
# Write hamiltonian
TS.SaveHS .true.
# LEFT ELECTRODE
TS.HSFileLeft ./elec-left.TSHS
TS.ReplicateA1Left 1
TS.ReplicateA2Left 1
TS.NumUsedAtomsLeft 5
TS.BufferAtomsLeft 5
# RIGHT ELECTRODE
TS.HSFileRight ./elec-right.TSHS
TS.ReplicateA1Right 1
TS.ReplicateA2Right 1
TS.NumUsedAtomsRight 4
TS.BufferAtomsRight 4
============================================= =====
==================================================
Sincerely,
MengQiu
> From: jose.torres.alo...@uam.es
> To: siesta-l@uam.es
> Date: Thu, 17 Jun 2010 15:43:02 +0200
> Subject: RE: [SIESTA-L] Who can help me!
>
> Dear Mengqiu:
>
> There might be systems (for example if you have a
> nanowire not periodic in XY) that they
> only require one K point in XY for the correct
> computation of the current.
>
> But in general you need to specify a dense enough
> mesh in XY. As you have already seen, there is an
> obvious dependance on the k sampling (Kx and Ky)
> since the Transmission(E) is computed by summing up
> the individual probabilities of transmission of
> all electrons incident with that total energy E.
>
> Now for a given energy E, there are many "incidence
> angles" (or Kx,Ky points) possible. So the sum to
> all electrons with total energy E translates into
> a sampling to all possible in cidence angles,
> i.e. a sampling to (Kx, Ky). The finer that sampling
> the better, but of course to save CPU time the correct
> thing to do is to test for convergence on that mesh, to
> make it just fine enough.
>
> In the examples you show probably the Kx,Ky mesh is
> not converged yet. (But it seems to me in any case
> that you are getting different expressions for a numerical
> "zero" for the current.)
>
> Yours
> --
> Jose A. Torres, Ph.D.
> SIESTA Manager
>
>
>
> On Thu, 2010-06-17 at 13:04 +0000, CaiMeng-Qiu wrote:
> > Dear Jose A. Torres：
> >
> > Thank you very much again!
> > I also several questions for these.
> >
> >
> > >
> > >
> > > On Thu, 2010-06-17 at 11:54 +0000, CaiMeng-Qiu wrote:
> > > > Dear Jose A. Torres：
> > > >
> > > > Thank you much for your explanation in detail.
> > > >
> > > > >
> > > > > - Also choose a large enough number of points to
> > > > > describe the function T(E) properly! (it may
> > > > > have sharp peaks)
> > > >
> > > > Do you mean I should adopt the dense k-mesh and large value of
> > > > TSTBT.NPoints?
> > >
> > > Here I just mean a TSTBT.NPoints to be large enough.
> >
> >
> > In the TRANSIESTA-manual, it mentions:" In the case of tbtrans, the
> > k-point sampling has to be specified also using a kgrid_Monkhorst_Pack
> > block, and can differ from the sampling that was used in the
> > TRANSIESTA calculation. The convergence of the transmission function
> > with respect to the k sampling can be slower than the one for the> >
> > density matrix. This means that one may have to increase the number of
> > k-points used in tbtrans." Did it mean that we adopt the dense k-mesh
> > for the tbtrans calcualtion after the Transiesta calculation?
> >
> > I do find that, for the special TSTBT.NPoints, the varied k-mesh in
> > the xy-plane generate the changed current.
> > For examplefor the tbtrans calcultions:
> > v -1.0 eV
> > TSTBT.NPoints 1500
> > k-mesh 6x6x50
> > I=-3.17E-16
> >
> > where:
> > v -1.0 eV
> > TSTBT.NPoints 1500
> > k-mesh 6x6x70
> > I=-3.17E-16
> >
> > where:
> >
> > v -1.0 eV
> > TSTBT.NPoints 1500
> > k-mesh 7x7x60
> > I=-2.94E-16
> >
> > where:
> > v -1.0 eV
> > TSTBT.NPoints 1500
> > k-mesh 8x8x60
> > I=-3.59E-16
> >
> > If i should check both the k-mesh and TSTBT.NPoints for the
> > calculated current?
> >
> > Thank you in advance!
> >
> > Sincerely,
> >
> > Mengqiu
> >
> > >
> > > >
> > > > Generally, how much is it for the value of TS.TBT.NPoints?
> > >
> > > A few hundreds to a few thousand points.
> > >
> > > >
> > > > Thank you very much again!
> > > >
> > > > Sincerely,
> > > >
> > > > Mengqiu
> > >
> > >
> >
> >
> >
> > ______________________________________________________________________
> > 使用新一代 Windows Live Messenger 轻松交流和共享！ 立刻下载！
>
>
使用Messenger保护盾2.0，支持多账号登录? ?现在就下载！
_________________________________________________________________
MSN十年回馈，每位用户可免费获得价值25元的卡巴斯基反病毒软件2010激活码，快来领取！
http://kaba.msn.com.cn/?k=1
