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Topics - baizq

Pages: 1 [2] 3
16
General Questions and Answers / Slater-Koster TB model for a self-defined system
« on: July 12, 2013, 16:38 »
Dear ATK developers,

I would like to make sure whether we can use the Slater-Koster method as implemented in ATK to model a somewhat complex system, e.g., the Ni/Graphene contact system in your paper PRB 85, 165442 (2012). The complexity may include the either contacted or freestanding regions of graphene, the metal edge, and the atomic position change due to relaxation, etc...

Best,
baizq

17
General Questions and Answers / noncollinear-spin functionality
« on: April 17, 2013, 13:03 »
Dear ATK developers，

May I know some background/theory stuff of the newly implemented noncollinear-spin funtionality? Say, the original papers you refer to about the noncollinear DFT. We are currently writing a paper and would like to include a few lines of simple description of the theory..but there is no tutorial for the functionality so far...

Thanks in advance!

baizq :)

18
General Questions and Answers / C60 modeling
« on: March 17, 2013, 17:26 »
Hi，

Here is a question about the C60 modeling: In VNL, how to align the centers of two opposite hexagons of a C60 fullerene molecule along the z axis of cartesian coordinates?

Thanks in advance!
baizq

19
General Questions and Answers / Error: BAD TERMINATION OF ONE OF YOUR APPLICATION PROCESSES
« on: January 20, 2013, 09:56 »
Dear all,

I was running a devce calculation when encountered such a problem: The program was killed right after equivalent bulk calculation and the following error message appeared:

Code
/home/z400/QuantumWise/atk-12.8.0/atkpython/bin/atkpython: line 7: 26207 Killed                  $EXEC_DIR/atkpython_exec $


+------------------------------------------------------------------------------+
|                                                                              |
| Equivalent Bulk  [Finished Sun Jan 20 13:03:08 2013]                         |
|                                                                              |
+------------------------------------------------------------------------------+

===================================================================================
=   BAD TERMINATION OF ONE OF YOUR APPLICATION PROCESSES
=   EXIT CODE: 137
=   CLEANING UP REMAINING PROCESSES
=   YOU CAN IGNORE THE BELOW CLEANUP MESSAGES
===================================================================================



I resubmitted the job and the same error was still there.

I am quite puzzled...Is it due to short of memory?

Thanks,
baizq

20
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

21
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


22
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

23
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

24
General Questions and Answers / system cannot be transformed to device configuration
« on: May 11, 2011, 11:18 »
Dear Colleagues,

I am following one tutorial of atk 11.2 : Spin transport in MTJ Fe-MgO-Fe, and encountered with an error as followed:

Error: the total width of the left and right electrodes may not exceed the width of the central region.

when I want to tranform the structure  from bulk configuration back to device configuration after geometry optimization.

Anyone knows what the problem is and how to solve it?

Thanks,
baizq

25
General Questions and Answers / Calculation the transport properties of graphene
« on: May 4, 2011, 16:38 »
Dear all,

is the anyone who has done calculation of the transport properties of bulk graphene using ATK? I have tried by using bulk graphene as electrode and bulk graphene(over 50 angstroms in the transport direction), but the properies look like nanoribbon, with quantized transmission spectrum. The IV curve is linear, which I think it is wrong. Is this because I use less kpoints or something wrong with setting?

help,help..............

26
General Questions and Answers / LDA+U for transport calculation
« on: April 22, 2011, 09:48 »
Dear colleagues,

Can we apply LDA+U (or GGA+U..or whatever+U) to transport calculation?

Thanks,
baizq

27
General Questions and Answers / SOI and spin-dependent voltage drop
« on: April 20, 2011, 04:32 »
Dear colleagues,

I have two questions:

1. Is spin-orbit interation taken into consideration by atk when we conduct a two-probe transmission calculation;

and

2. Can we calculate spin-resolved voltage-drop with ATK 11.2?

Thanks,
baizq

28
General Questions and Answers / iv calculation with ATK 11.2
« on: April 8, 2011, 14:29 »
Dear colleagues,

Is there anybody who knows how to calculate iv characteristics of a two-probe device with the new version ATK 11.2? Do we need a seperate script?

Thanks.
baizq

29
Installation and License Questions / trouble in starting VNL
« on: March 12, 2011, 13:44 »
Dear all,

I have installed ATK 11.2 combined with VNL, and loaded a trial license for OPENSUSE 11.3 Linux x64 system. I have found that it is ok for atk command-line mode, but when I want to use the graphical interface, VNL cannot be started. It does not give any error information either, just no response.

So what is the problem? Is it necessary to activate the ATI graphical card in our workstation, instead of using the default one of the system, to run VNL?

Thanks.
baizq

30
General Questions and Answers / how to treat lattice mismatch of a GMR junction
« on: March 7, 2011, 08:21 »
Dear colleagues,

How to treat the GMR junctions, of which the electrode and space layer have a lattice mismatch?

For example, in Co/Cu/Co spin valve, the lattice constant of fcc Cu is 3.615A, whereas it is 3.5447A for fcc Co. There is around 2% lattice mismatch. How should we deal with this? It is correct to compress the lattice constant of Cu spacer to the same value as Co (force Cu lattice constanct to be 3.5447A)? Will this method lead to large error?
Or should we conduct a relaxation first to determine all geometry factors of the system, such as the lattice constancts of both spacer and eletrode, the distance between the last screening layer and the first space layer, and so on....

Thanks
baizq

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