Messages

61

Scripts, Tutorials and Applications / Re: I-V curve tutorial problem

« on: May 7, 2012, 12:34 »

Apologies, a small typo in the script, which was updated recently, caused this. Try again - should be fine now.
 
When downloading the script again, make sure you don't get a local cached version. The mistake was on line 8, which should have been

Code: python

configurations = [configurations[j] for j in numpy.argsort(biases)]

Yes, I have also encountered the same error and this modification solves the problem. Why not changing the iv-curve and voltage-drop tutorial as well...

Besides...just for kidding, why my account level drops from heavy ATK user to regular ATK user...

62

General Questions and Answers / PDOS and TDOS

« on: December 15, 2011, 10:14 »

Dear all,

We have noticed that the current version of ATK can calculate PDOS and project the density to s, p, d or f orbitals of certain atom. The question is whether it is possible for us to make an even finer investigation by analyzing the projection on s, px, py, pz, dxy, dyz, dzx, dx^2 and dz^2 orbitals?

Another question is whether it is possible to calculate the tunneling DOS for a Fe-MgO-Fe like MTJ system using ATK.

Thanks,
baizq

63

General Questions and Answers / Re: geometry optimization as device leads to unreasonable results

« on: September 28, 2011, 10:57 »

could you also attach the log file, this will speed up our handling of this case

Hi kstokbro,

I have tried to attach the log file, but the one I got is as large as 8 Mb which far exceeds the limitation....

The program runs for 117 iterations but the force and stress still can not reach to convergence.


baizq

64

General Questions and Answers / geometry optimization as device leads to unreasonable results

« on: September 28, 2011, 05:14 »

Dear colleagues,

Recently I am conducting geometry relaxation of CoFe-MgO-CoFe (Fe-O interface) MTJ when encoutered a problem: when the MTJ is relaxed as device with constraint on c-axis of the cell removed, the result seems unreasonable. The interfacial Fe-O distance, which is set to be 2.23 A as initial value, keeps increasing to more than 3.7 A. Convergence is also hard to reach so I have no choice but to stop it.

I would like to know whether it is due to my inappropriate parameter settings. 

Attached is the script for geometry relaxation. I cannot attach the trajectory.nc file due to attachment size limitation.

Thanks!

baizq

65

General Questions and Answers / Re: negative k-resolved transmission coefficient

« on: September 22, 2011, 18:01 »

Dear nori and Anders,

Yes, the negative values are eliminated by using RecursionSelfEnergy. Thank you so much for your help. 

baizq

66

General Questions and Answers / Re: negative k-resolved transmission coefficient

« on: September 21, 2011, 08:22 »

ATK uses the Krylov method by default because it's faster, but sometimes it can give negative DOS or transmission, in which case you had better switch over to e.g. the RecursionSelfEnergy method.

To get the coefficients out in the new version is very easy, as proven by the fact that you have plotted the data already - so you have the numbers It's basically a matter of

Code: python

t = nlread("file.nc",TransmissionSpectrum)[0]
values = t.transmission()

then values will be a list data[n][e][k], where n, e, k are integers looping over the number of spins, energies and kpoints.

Hi Anders,

Thanks very much for your help.

What is the difference between Krylov and Recursion.... Is RecursionSelfEnergy more accurate than Krylov?

baizq

67

General Questions and Answers / Re: negative k-resolved transmission coefficient

« on: September 21, 2011, 08:18 »

Is there any physical meaning for a negative transmission coefficient?

No, always the negative transmission coefficient in ATK is an artifact or due to bugs.
I feel the magnitude of negative coefficients is relatively large so it may be better that you use DirectSelfEnergy or RecursionSelfEnergy instead of KrylovSelfEnergy.

Hi nori,

Thanks so much for your kind help.

Should I use DirectSelfEnergy or RecursionSelfEnergy for the self-consistent calculation or just for transmission spectrum calculation after scf? 

 
baizq

68

General Questions and Answers / negative k-resolved transmission coefficient

« on: September 19, 2011, 16:17 »

Dear colleagues,

I was calculating the transport properties of a MTJ structure when something strange happened. I got a k-resolved transmission coefficient spectrum which contained some k points with negative values. Please see attachment...

Is there any physical meaning for a negative transmission coefficient? Or why it happend?

BTW, is there anybody who has the script to extract the k-resolved transmission coefficients from the .nc file? I remember there was a script for the older version of ATK...

Thanks so much!
baizq

69

General Questions and Answers / Re: complex band structure

« on: June 10, 2011, 03:12 »

Dear Anders,

Yes, it is always struggling when going deeply into theoretical area. Thanks very much for your efforts.

baizq

70

General Questions and Answers / Re: complex band structure

« on: June 3, 2011, 13:30 »

Thanks. Hope it will come soon.

71

General Questions and Answers / Re: complex band structure

« on: June 2, 2011, 10:35 »

Hi Anders,

Is there any full tutorial for complex bandstructure calculation?

By the way, I know how to get K-dependent transmission coefficient with ATK. However, can we calculate K-dependent DOS for a two probe system?

baizq

72

General Questions and Answers / Re: about specifying magnetization direction for electrodes of a two-probe system

« on: May 21, 2011, 21:03 »

Well, got it, thanks, zh.
Hope the noncollinear DFT will be realized soon.

baizq

73

General Questions and Answers / about specifying magnetization direction for electrodes of a two-probe system

« on: May 21, 2011, 03:37 »

Dear Colleagues,

Can we set the magnetization of electrodes to a specified direction in ATK, say, is it possible to constrain the magenetization parallel to the transport direction of the device?

Alternatively, what is the mechanism embedded in ATK for the simulation of magnetization direction of the electrode? Will the direction automatically converge to the easy axis of the material by the algorithm?

Many thanks! 
baizq

74

General Questions and Answers / Re: system cannot be transformed to device configuration

« on: May 13, 2011, 09:50 »

Wow...That's pretty fine. Yes, I am using VNL 11.2.0 now and I will upgrade it to ver. 11.2.2.
Thanks, nori. 

75

General Questions and Answers / Re: system cannot be transformed to device configuration

« on: May 13, 2011, 06:01 »

Ok...I have modified it..Thanks..
So I do not have to add iteration_control_parameters = NonSelfconsistent to electrode calculator, right...?

Thanks!