Messages

1

General Questions and Answers / Re: Interfering and non-interfering contributions of the transmission function

« on: May 23, 2024, 13:06 »

Thank you! I'll give a try.

2

General Questions and Answers / Interfering and non-interfering contributions of the transmission function

« on: May 3, 2024, 19:18 »

Dear QuantumATK community,

is it somehow possible by accessing and manipulating low-level entities, to get interfering and non-interfering contributions from the Transmission function as done in the following equations (5-8) from this paper: https://doi.org/10.1063/5.0141577

Moreover, is it possible to get each individual contribution of molecular orbitals to the transmission, and their phase (eqs 9-11)?

Thank you very much,
Chiara

3

General Questions and Answers / Transmission as function of electrode Fermi level

« on: March 15, 2023, 19:45 »

Dear QuantumATK community,

I would like to support my single molecule STM-BJ data with DFT calculations.
I got a certain value of conductance at break-off distance from STM-BJ measurements, this should correspond to the fully streatched molecule between the two electrodes (substrate and tip).
I run DFT+NEGF simulation (GGA, PBE, DZP and SZP for Au atoms) and I compared the experimental conductance value with the transmission value at the fermi level (0 eV)  multiplied by the quantum conductance G0 (G=G0*T(Ef)), Ef fermi level).
The theoretical conductance G and the experimental one differ of order of magnitude.
This is related to different experimental configuration of electrodes w.r.t. the ideal device configuration for the theoretical calculation, and thus also to different electrode fermi levels w.r.t. the ones computed by the LCAO calculator.

So, I would like to compute only the transmission value at the fermi level (T(0 eV)) by varying the value of electrode fermi level w.r.t. the one obtained with QuantumATK, to understand approximately which value of electrode fermi level provides a good match with the experimental conductance value.

How I can force the value of the electrode fermi level in the transmission calculation starting from a DeviceConfiguration already obtained with LCAO calculator?

Thank you.
Best wishes 

4

General Questions and Answers / Computational time estimation for NEB?

« on: May 16, 2022, 09:43 »

Dear QuantumATK staff,

I launched few days ago a NEB calculation for 7 images of a geometry containing 29 atoms (32 CPU).
The simulation is still running, and I would like to estimate more or less how much time is still required by inspecting the log file. Is there information to understand it?

In attachment the .py script and log file.

Thank you,
Regards

5

General Questions and Answers / DeviceLCAOBuilder' object has no attribute 'createMatrixCalculator'

« on: February 11, 2022, 11:38 »

Dear ATK community,

in running into trouble with the function vectorToGrid. In particular by typing:

vectorToGrid(eigenvector, device_configuration)

the following error occurs:

File "utilities.py", line 17, in vectorToGrid
matrix_calculator = builder.createMatrixCalculator()
AttributeError: 'DeviceLCAOBuilder' object has no attribute 'createMatrixCalculator'

Attached the script I'm running in 2021 version.
Any help?

I really thank you,
Best regards

6

General Questions and Answers / Practical meaning of the 'CELL' object?

« on: June 20, 2020, 13:51 »

Hi QATK community!

I have a trivial question: what is in practical terms the meaning of the cell (continuous white lines in the attachment) ? Is related to the basic unitary cell (crystallography) or more in general it represents the simulation domain where the calculator performs its analysis?

I mean: if I have to simulate for e.g. a FET I have to include in the cell all the objects that influence the transport (like in the attachment: gate and electrodes) or I can for example leave out the gate terminal? And what changes in the two different cases from a computational time standpoint and in the resulted IV curve?

Thank you for your kind attention

7

General Questions and Answers / Poisson solver for molecular FET device?

« on: March 15, 2020, 19:57 »

Hi, I want to analyze transport in a molecular FET device but I don't know what type of Poisson solver it's the most suitable in this case, and what boundary conditions I should use. I attach the geometry.