Topics

1

General Questions and Answers / What do we get with MolecularEnergySpectrum for a two-probe system?

« on: August 28, 2017, 08:14 »

We can set a device configuration for the parameter "configuration".  But what will we get with MolecularEnergySpectrum for a two-probe system? The MPSH? We diagonalize the the Hamiltonian of the central region? Since the Hamiltonian is no Hermitian for a two probe system, what will be the wave functions? The real part?

2

General Questions and Answers / About transmission eigenstates

« on: May 13, 2016, 05:38 »

From here: http://www.quantumwise.com/documents/manuals/latest/ReferenceManual/index.html/ref.transmissioneigenstate.html

we are told that the transmission eigenstates are linear combinations of Bloch states of the electrodes.  However, I think this definition about transmission eigenstates there is wrong or at least misleading or confusing. Obviously, the Bloch states only belong to one electrode. With the Bloch state of only the left electrode, we can not get the spatial distribution of the transmission eigenstate in the central region and the right electrode since these Bloch states are not defined there.  Thus, I think, the transmission eigenstates are the linear combinations of the scattering states which are distributed in the whole space and span a Hilbert space. The scattering states  are defined by equation (4.1) in Jeremy Talor's PhD thesis.

Please correct me if I am wrong and please give a more detailed description or introduction about it. Many thanks.

3

General Questions and Answers / For some understanding about the gate voltage

« on: September 12, 2013, 10:33 »

Hello, Dear All,

I am thinking about the gate voltage. Now we can add a metallic region or a dielectric region to the the central region. I want to know, what is the difference between this new method and the old method of shifting the onsite energy (like in version 08.10)? By the way, in the old method, do we just change the diangonal terms H_ii, but not the off-diagonal terms H_ij?

Thanks.

4

General Questions and Answers / about restart from a previous calculation

« on: September 26, 2010, 15:48 »

Dear all,

I have done a calculation with LDA. Now I want to use the converged electron density as an initial electron density for a GGA calculation.  Of course, I have to use restoreSelfConsistentCalculation("twoprobe-scf.nc") to restore the initial density.

My question is:  when I do the GGA calculation, will the lead part be calculated with GGA again or just use the LDA result? I mean, will the lead part be recalculated?

Thanks.

5

General Questions and Answers / Is the convergence considered for the denxity matrix or the charge density?

« on: September 15, 2010, 16:04 »

In siesta, the convergence is considered for the density matrix. In ATK, is it considered for density matrix or the charge density at each point in the real space? Thanks a lot.

6

General Questions and Answers / Spin polarized calculation

« on: April 1, 2010, 15:04 »

Hi,

It is very interesting to see that even if I set initial_scaled_spin=[0.0]*32 in electronDensityParameters( ), i.e., when I set the initial of the spin of each atom to zero, it still performs a spin polarized calculation.

It seems that, if we want to do a non spin polarized calculation, we should not set the option initial_scaled_spin at all, even if it is 0.0.

Is it correct?

7

Scripts, Tutorials and Applications / How to do parallel in analysis?

« on: March 30, 2010, 04:16 »

Hello, Dear all,

I want to do parallel in analysis, e.g., in the calculation of the transmission or LDOS. However, when I use more than 1 processors, it seems that each processor do the same job separately and print the same information to the standard output. This makes the output very messy. So I have two questions here:

1. Can we do parallel in analysis?

2. If we can,  how can we print information from only one processor in the python script, say, node 0, please?

Thank you very much!!

8

General Questions and Answers / Reflection coefficient

« on: May 10, 2009, 03:23 »

Hello, everybody,

This is not related to the usage of ATK and VNL. But I jut want to discuss with you about the problem of the calculation of reflection coefficient.

It is well known that transmission from left lead to right lead is calculated by T=Tr(Γ_L*G^R*Γ_R*G^A). And the reflection can be simply obtained by R=1-T.  However, I want to know, whether we can get it by R=Tr(Γ_L*G^R*Γ_L*G^A)?

I just want to understand something about the Landauer formula. Your answers are greatly appreciated.

9

General Questions and Answers / always stops after "Equivalent Bulk Calculation (Initial Density for TwoProbe)"

« on: March 27, 2009, 02:29 »

Hello, Dear All,

My calculations always stops after tens of steps of "Equivalent Bulk Calculation (Initial Density for TwoProbe)". This happens very frequently and it does not give any error messages.  Do you know why, please?

10

General Questions and Answers / How to set up initial magnetic moment for each atom in ATK 2.0.4?

« on: March 18, 2009, 04:57 »

From the manual of ATK 2.0.4, we can know that we can set the total magnetic moment for the whole system. However, I want to set up an initial magnetic moment for each atom or for some of them. Does anybody know how to do it, or is it possible to do it,  please?