Messages

1

General Questions and Answers / Re: How do I save the GUI inteface in the QATK Script Generator

« on: December 22, 2020, 05:50 »

You may use Templates in the GUI, as described in this guide, https://docs.quantumatk.com/guides/scripter/templates/templates.html.

Hello, Petr!

May I use a script langugae to substitute the window operation? I guess there was a python object to do this and I could use it to generate a new scripte file for ATK. This function can really reduce the work for high-throughput screening.

2

General Questions and Answers / Transmissions associated with different molar states

« on: February 5, 2020, 13:19 »

Dear quantumatk staffs and users,
      Please see the figure in the attachments (DOI: 10.1103/PhysRevLett.109.056801). There are two states (I think they can be obtained from a MPSH analysis) in the (e), and the individual transmission functions associated with the two states are displayed in the (f). My  question is that if we can calculate the transmission spectrums  associated with different states using QuantumATK, or this can be realized by a python script.

3

General Questions and Answers / Re: Can we consider van der Waals interations in device simulation？

« on: December 29, 2019, 03:20 »

Got it! Thanks for your patience and wisdom.

4

General Questions and Answers / Re: Can we consider van der Waals interations in device simulation？

« on: December 28, 2019, 06:26 »

And if that's impossible in principle. How should we treat these papers that considering the van der Waals interations in device simulations using QuantumATK. (One of my friends is reviewing one of them  . It really troubles him)

5

General Questions and Answers / Can we consider van der Waals interations in device simulation？

« on: December 28, 2019, 06:19 »

Dear QuantumATK staffs and users:
  Happy new year! I have read some papers using QuantumATK software. Some of the authors stated that they have considered van der Waals interations in their device simulations.    And one of the authors said he have included the van der Waals interation in his calculations even using the semi-emprical Extended Huckel calculator. I think it is really amazing!  As known, QuantumATK give a online tutorial about the DFT-D method and the basis-set superposition error .(https://docs.quantumatk.com/tutorials/dispersion_corrections_and_bsse/dispersion_corrections_and_bsse.html) This is very helpful to understand the interaction between atomic layers. What's more, it tell us the existence of the so-called basis set superposition error (BSSE). I have tested the DFT-D method combined with the counterpoise correction in my device simulations. I have used the GGA and Pesudo Dojo parameters (with version 2018.06-SP1). The log file give a warning that  DFT-D is not included in the device simulation. I have to give up a good idea. That's why I am so amazing about the above papers. Maybe I have written the scripts in a wrong way. And I want to know whether we can consider van der Waals interations in device simulation. If that's possible, can someone give a help document or a script file. I will appreciate you sincerely. If that's impossible, can the QuantumATK engineer complete this function in the next version? (I know nothing about the  implementation of NEGF. If that's too difficult or impossible in principle, please fell free to tell me)

6

General Questions and Answers / Re: Different potential profiles of the same MOSFET from LCAO and DFTB calculators.

« on: October 29, 2019, 05:11 »

Thanks for your advice. You are right! Metal gate work function should be considered to  imitate the electrostatic potential between the gate and channel.

7

General Questions and Answers / Re: Different results of MOSFETs from LCAO and DFTB calculators.

« on: October 25, 2019, 15:58 »

I have attached the run scripts and logs in this reply If someone is interested with this phenomenon, this will be helpful.

8

General Questions and Answers / Different potential profiles of the same MOSFET from LCAO and DFTB calculators.

« on: October 25, 2019, 15:54 »

Hello, laborious quantumatk staffs and users, thanks for your attention with this topic.
    I met a problem with the simulation of graphene-nanoribbon-based MOSFET. The device diagrams are attached. This is a typical double-gate device model. The thickness and relative dielectric constant of top and bottom oxide layers are 1 nm and 3.9, respectively. (I have assumed that the graphene layer is of no thickness. For more precise simulation, one must confirm the dielectric constant of graphene nanoribbon. As far as I know, it is still an open question) And the electrodes are n-doped. For simplification, a very small device demo is shown, but it does not influence the final result. I have simulated this structure using both LCAO and DFTB calculators. The Parallel Conjugate Gradient Poisson solver is adopted with Neumann boundary in the AB direction and Dirichlet boundary in the C direction. (Multi-grid always reports a residual warning and is really computation-expensive) Distinct results are attached. It is amazing that the gate almost has no effect on the potential profile computed by LCAO calculator. I know the electrostatic control of the gate is dramatically reduced due to the short channel effect. But the same configuration computed by DFTB calculator show an evidently better electrostatic control of the gate. And the difference becomes more obvious in a long MOSFET model according to my previous calculations.
    The LCAO-DFT calculation has considered more electronic states compared to the DFTB calculation. May this account for this? But I think that there should be the same (or similar) number of net charge in two kinds of calculations and thus the electrostatic control of the gate should not be distinct. Can anyone give me some tips?

9

General Questions and Answers / Re: What‘s the difference between the PDOS of a bulk and the PLDOS of a device?

« on: August 19, 2019, 11:26 »

 Hi, it is me again. I have carefully read the manual about the DeviceDOS in ATK.(https://docs.quantumatk.com/manual/Types/DeviceDensityOfStates/DeviceDensityOfStates.html)
I found this sentence "The DeviceDensityOfStates (DDOS) D(E) is computed via the spectral density matrix ρ(E) = ρL(E)+ρR(E) (cf. The non-equilibrium Green’s function (NEGF) method) where L/R denotes the contribution from the left/right electrode".
I then read the munual of NEGF method.(https://docs.quantumatk.com/manual/NEGF.html#sect2-negf-greenfunction) I found this one "The left density matrix contribution is calculated using the NEGF method as [BMO+02]
DL=∫ρL(ε)f(ε−μLkBTL)dε, whereρL(ε)≡12πG(ε)ΓL(ε)G†(ε)is the spectral density matrix. Note that while there is a non-equilibrium electron distribution in the central region, the electron distribution in the electrode is described by a Fermi function f with an electron temperature TL." I think the Fermi function f causes the difference in the question, right?

10

General Questions and Answers / What‘s the difference between the PDOS of a bulk and the PLDOS of a device?

« on: August 19, 2019, 10:14 »

  Dear staffs and users:
 I have a question that really troubles me. I have no idea about the difference between the PDOS of a bulk and the PLDOS of a device, even though I know they don't look quite the same.
I have analyzed two similar quantum dot systems. The first one is a bulk system. The second one is a device system, whose central region is just the same as the bulk one. The extended electrodes are semiconductors. Thus the Fermi level of the electrode locates at the central of forbidden gap. 
The presented difference  is that these discret energy levels in the bulk system can be recognized through its PDOS, but these discret energy levels in the device system can not be recognized though the PLDOS. These discret energy levels are lying the energy range of the forbidden gap of electrodes, and thus they can not be founded in the transmission spectrum. I then tuned the scale of the PLDOS into 'log' format. I did find these discret energy levels, but they are really fuzzy to apart from the background DOS. It means that the PLDOS corresponding to these discret energy levels are very small.  But in a bulk system, the PDOS corresponding to these discrete energy levels are almost the same large as these continuous bands. Is the gap of electrodes cause this difference? But in the bulk system, the quantum dot is also sandwiched by this kind of semiconductor. I really want to know the reason.

11

General Questions and Answers / Re: Submit Bug

« on: July 18, 2019, 15:51 »

My pleasure.

12

General Questions and Answers / Submit Bug

« on: July 18, 2019, 05:25 »

The  "projections=ProjectOnTags" produce a wrong result in DOS(PDOS, fatbandstructure) calculation.
 I set two different tags in my scripts. Then, I calculated their PDOS. I got obvious wrong results. The same the fatbandstructures are (see the attached figure). This error is believed to only occur in ATK 2019 (In addition, the other projections, such as "projections=ProjectOnElement" works well). Because when I test the same script in ATK 2018, I got the correct results.

13

General Questions and Answers / The transmission spectrum of bulk and device system

« on: March 5, 2019, 08:05 »

Dear all,
   In ATK, both the bluk and device system can produce a transmission spectrum. In the device system, the transmission can be calculated by the Green function in the framwork of NEGF. While the transmission of bulk system seems to be related with the complex band structure. Adjacent cells are taken into consideration in the calculation procedure. If the atomic structure of a bulk system is the same as the central scattering region of another device system, and the resistance of the electrode region in device system is negligible, will we get the same transmission results? If not, how to understand the difference?
Thanks,
your Shizhuo.