Messages

1

General Questions and Answers / Re: convergence problem

« on: June 5, 2017, 06:30 »

zero bias calculation is converging well, but when I gave some bias the job stopped after some time without showing any error.

meet the same problem.. 

2

General Questions and Answers / Is the electrode must be rectangular in a 2D materials based MOSFET?

« on: September 29, 2016, 13:12 »

Can we use a 2D lattice which is not rectangular when we build the electrode of a MOSFET in atk?

3

General Questions and Answers / can I understand the EDP as conduction band or vanlence band edge?

« on: May 9, 2016, 12:57 »

Dear all,

In the Device Density of States section of the page http://docs.quantumwise.com/tutorials/silicon_pn_junction.html, there are 3 figs showing the projected DDOS and electrostatic difference potential (EDP) (see below). Am I right to regard the EDP as the conduction or vanlence band edge?
 

thanks!

4

General Questions and Answers / Re: fixed spin in transport calculations?

« on: March 21, 2016, 15:35 »

Has this problem been resolved?Is it possible to do a reliable transport calculation with SOC (NEGF+SOC) using ATK now?

Dear all

I have recently managed to perform fixed-spin calculations (angle of the spin set to a given value) for an Iron wire with SOC (OMX pseudo/basis)
For the moment it is only a "standard" DFT calculation with "BulkConfiguration"
I could set the spin orientation by using the following script (taken from FeMgO.py)
==================================================
B0 = 5*eV
theta=30*Degrees   
#----------------------------------------
# Intial spin
#----------------------------------------   
spin_list = [(Iron, 1, theta, 0*Degrees)]
initial_spin = InitialSpin(scaled_spins=spin_list)
spin_list = [(Iron, theta, 0*Degrees)]
fixed_spin = FixedSpin(spin_list, B0)

bulk_configuration.setMagneticField(fixed_spin)
=========================================================
The calculation works perfectly fine. In particular I am able to follow the evolution of the band-structure with the angle between spin and wire axis...

I now try to do the same type of calculation but in transport (DeviceConfiguration) in order to study the evolution of the transmission with the angle of the spin (AMR),
But my calculation crashed.

Is the option .setMagneticField(fixed_spin) available in DeviceConfiguration?

Thanks in advance

Cyrille

5

Scripts, Tutorials and Applications / Re: question about the script of Fermi surface and spin directions

« on: March 21, 2016, 14:48 »

Great!!! Thank you very much for the help!!!

6

Scripts, Tutorials and Applications / Re: question about the script of Fermi surface and spin directions

« on: March 19, 2016, 06:44 »

thank you for the reply!
I cannot upload the nc file in the forum possibly because of its big size... please check the file from the link below:

https://onedrive.live.com/redir?resid=5B2623E5F1D7B0A5!587&authkey=!ALWErhZCPUr1DQ8&ithint=file%2cnc

7

Scripts, Tutorials and Applications / question about the script of Fermi surface and spin directions

« on: March 17, 2016, 16:24 »

Dear all,
I'm very interested in the recent tutorial about Bi2Se3. Following the script, I want to plot the fermi surface and spin directions around the Dirac point 'K' in graphene (not the gamma point in Bi2Se3).  Attached is the changed script and what I get. In the figure using conduction band (the 8th band), I can see a spin pattern which is not very orderly.  There is even no "arrows" in the figure with valence band ...
I think I've made some mistake when I change the script. Can anyone help me to checkthe scripts?

8

General Questions and Answers / charge redistribution between lead and middle parts

« on: March 4, 2013, 08:38 »

hello， everyone！
someone tells me that：
The NEGF formalism implemented in ATK package actually does not take into account the charge redistribution between resistive region in the middle and lead parts in the left and right sectors of the system because the lead Hamiltonian is just put into the self energy of the formalism as it is.

Is this statement right？ Is there any method to improve?

Looking forward to hearing from you
have a good day!!

9

General Questions and Answers / question about atoms projected band structure

« on: October 23, 2012, 14:10 »

I have tested the new function of band structure projected on atoms in ATK 12.8.b2, but found that the projected band structure cannot coincide with the band structure of the combined system.
For example, I calculated the band structure of the Al adsorbed graphene monolayer. The band structure projected on the Al atoms does't belong to that of  the combined system.

10

General Questions and Answers / The difference of the gates in FET

« on: April 6, 2012, 08:05 »

I noticed that there are different types of gate in FET devices. one is the gate that locates only above or below the channel; the other one is the gate that locates over all the device (that is not only the channel but also source and drain).
Does anyone know the difference of these two? Or is there any paper about these topics?