Topics

1

General Questions and Answers / Bias direction for different electrodes

« on: August 27, 2024, 09:29 »

Hi,

I have tried looking through the forum but I couldn't find an answer to my question.
I am investigating the difference between a molecular junction with two Au electrodes and a molecular junction with Au and Al.

Doing so I ran into a definition problem of the forward/reverse current and the chemical potential for the Au-Al junction. It seems that  in this case the Au (left) is kept at 0 and Al(right) is changed.

A forward bias is defined as VL > VR (that being the voltage of the left electrode is higher than of the right)
in the same line the chemical potential is like this: uL < uR.
When I look at the uL given in the transmission spectra (as I understand is the fermi level of the left electrode) at postive 1V I get that uL = 0 and uR = -1.  But this would be uL > uR - so actually reverse bias?

In general I get:
positive 1V: uL=0 , uR = -1
negative 1V: uL=0, uR = +1

I am a little confused here, could you help clarify this for me?

I have attached the note from the tutorial that I tried using to understand this.

Thanks in advance.

2

Scripts, Tutorials and Applications / 1D projector sum, average and line

« on: June 13, 2024, 09:38 »

Hi,

I am using the 1D projector in quantumATK to visualise different things. In that regard I got confused reading the forum as well as the tutorial as to how I should understand the different projections.

In this tutorial (https://docs.quantumatk.com/tutorials/atk_transport_calculations/atk_transport_calculations.html) it is written as "With this tool you can project a potential or density along a certain direction, integrated or averaged over the two directions perpendicular to it. "

But in this post (https://forum.quantumatk.com/index.php?topic=9735.msg32591#msg32591) from 2022,  it is not an integral " It's not an integral over the perpendicular direction, just a sum or average."

So my question is, how do you calculate/how should I understand, the sum, average and line in the 1D plot? 

Thanks in advance,

Louise

3

General Questions and Answers / Orbital coefficients

« on: May 2, 2024, 13:14 »

Hi,

Is it possible somehow to get the orbital coefficients out when calculating the eigenstates of a molecule?

I cannot find anywhere in the documentation that mentions this, so it might be that you call it something else.

thank you in advance,

Louise

4

General Questions and Answers / Dipole moment calculation

« on: August 29, 2022, 13:25 »

Hi,
I am trying to understand how to calculate the dipole moment of a molecule (or a junction).

I have used the two exact script that you put on the manuel for the electron density. https://docs.quantumatk.com/manual/Types/ElectronDensity/ElectronDensity.html   nh3_density.py and nh3_density_multipoles.py

Everything is running, my problem is the results.  I get the result shown below. I am aware that the dipole is a vector and that the length of the vector should be the dipole moment. But both the unit and the size of the dipole moment does not make sense. Could you help me understand how this works?
Why is it Bohr**4*e when the unit is e*bohr? (for the dipole)
And when I convert the length of the vector to Debye (1 Debye = 0.39 e*bohr) the dipole moment is no where near comparable with results from e.g. Gaussain. 

Thanks in advance.

----------------------------------------- output from nh3_density_multipoles.py ---------------------------------------------------
center of mass (bohr)  =  [ 10.56827806   9.91727343   9.60194572] Bohr
monopole   (e)         =  8.00000122768 Bohr**3*e
dipole     (e*bohr)    =  [-9.02093396e-16 -2.84059249e-14 -1.58800480e-14] Bohr**4*e
quadropole (e*bohr**2) =  [[ 1.88237189e+01 -8.12198595e-06 -1.01224738e-05]
 [-8.12198595e-06  1.88237184e+01  7.58701761e-05]
 [-1.01224738e-05  7.58701761e-05  1.61672803e+01]] Bohr**5*e