Messages

1

General Questions and Answers / Re: regarding to band structure

« on: April 5, 2011, 15:49 »

Probably they don't use exactly this kind of geometry. For a band structure to make any sense, the structure needs to be periodic, there is no way around that

2

General Questions and Answers / Re: regarding to band structure

« on: April 5, 2011, 15:09 »

Your structure is not periodic along Z, so you can't expect to get any sensible results from a band structure calculation like that. In fact, it's not periodic in any direction at all, so it's like a molecule, so the result will be flat lines (molecular levels, sort of).

No offense my friend, but it would be a good idea if you study in a basic theory book what a band structure is. You need to understand the Brillouin zone concept, and the relation between the symmetry points like G,Z and the periodicity of the geometry.

3

General Questions and Answers / Re: length and width measurement

« on: March 23, 2011, 12:18 »

Eh, is what possible? If you have specified the ribbon, you know all the coordinates and so also exactly how large it is already

4

General Questions and Answers / Re: Effect of long range forces in cnt interaction

« on: March 3, 2011, 10:23 »

I don't understand why you say it doesn't change. Clearly there is a minimum somewhere around separation 2.5-3 Ang. Of course the total energy will not vary much at all once they are completely separated, out around 5-6 Ang. Just focus on the area between 2 and 3 Ang and scan in steps of 0.1 Ang or small, and you will most likely have a very nicely defined minimum.

5

General Questions and Answers / Re: Help! How to calculate the TMR values of Co2MnSi/MgO/Co2MnSi MTJ?

« on: January 24, 2011, 09:37 »

The TMR is defined from the conductance rather than the current, and the conductance is well-defined even at zero bias.

6

General Questions and Answers / Re: electrostatic difference potential

« on: November 30, 2010, 19:31 »

Maybe a virus attack I'm joking, my friend, I'd love to help you figure it out, but it's pretty impossible without at least an error message, the log file, and ideally the input file too

7

General Questions and Answers / Re: Finding BandGap

« on: November 27, 2010, 13:20 »

Your question is quite confusing Please provide (much) more details, like scripts, plots, etc.

8

Scripts, Tutorials and Applications / LiH2 voltage drop

« on: November 27, 2010, 13:19 »

You probably just made a small mistake. But since you don't share any details, like the scripts you are running, it's impossible to figure out.

9

General Questions and Answers / Where is my NC file?

« on: August 23, 2010, 14:25 »

I'm using VNL 10.8, and I ran a calculation by dropping the script on the the Job Manager. But I forgot to specify the full path of the NetCDF file, and now I can't find the file - where is it???

10

General Questions and Answers / Re: DOS for bulk

« on: June 25, 2010, 10:24 »

the script is download from there, I only modify the filename.nc.

Which is why I asked you to attach the script. You probably changed it in a way that makes it not work. For instance, if you wrote "C:\users\me\file.nc", this will not work on Linux. Or if the file is not in the same directory as where you run it. Or several other things. Nobody can guess what's wrong with the script unless they can see it  

Also, when you say it doesn't work, there are many ways it can fail. Are there any error message? Do you get an empty file? Is there a file but no results?  

I'm not writing this to be impolite or rude. We are many users on this Forum who are happy to help other users, but to do so, a certain amount of information is needed. Otherwise you will simply not get any answers to your questions. So in any situation where there is a problem with a script, post the script. And if something doesn't work, tell how it fails, not just that it fails. Any messages printed from the program should always be included in the post.

If everyone does this, questions can be answered faster and we can all be more productive doing what we enjoy, i.e. doing nice science with ATK

11

General Questions and Answers / Re: DOS for bulk

« on: June 24, 2010, 09:14 »

In all friendliness, unless you post the script that doesn't work, how do you expect anyone can help you?

12

General Questions and Answers / Different mesh cut-off for analysis?

« on: November 27, 2009, 16:22 »

As far as I understand, ATK uses the mesh cut-off used in the calculation to determine the grid for electron density and other 3D quantities that we can compute in the post-scf analysis step.

However, sometimes I think it would be nice if one could specify a different mesh cut-off for e.g. Bloch functions. For instance, if I use a very small mesh cut-off for nanotubes, but I would like better resolution for the grids. Conversely, sometimes you need a very large mesh cut-off to converge the SCF loop, but then the grids take up too unnecessarily much memory.

So, the question is, how about we could specify a separate mesh cut-off for the 3D grids?

13

General Questions and Answers / Re: Can anyone tell me is the calculated results right or not?

« on: November 25, 2009, 11:58 »

To understand why you get the results you see is precisely your task as a researcher.

Yes, the results are correct - ATK has computed the correct results based on your input. Your real question should be "is the input correct", and again, only you can answer that as only you know what you are trying to compute.

The community can help you with by providing some insight into specific questions, like "is 3x3x1 appropriate k-point sampling" or "do I need a very large mesh cut-off for gold", etc. But I don't think it's appropriate to ask someone else to do your research for you.

14

General Questions and Answers / Re: Can ATK be used to study the weak connected molecule?

« on: November 11, 2009, 15:06 »

Which, however, is not to say that ATK cannot be used for your system. What the referee asks, is how do you know that your system is not weakly coupled. A simple answer is that you assume that it isn't... A more complete answer, which probably might be needed, can only be found by you - nobody else knows what your system even looks like. By providing such an answer you will show the referee that you understand what you are studying. This doesn't mean that you need to understand all the basic formalism that ATK uses, except as zh writes, that ATK assume the system is bonded, and not weakly coupled.

15

General Questions and Answers / Re: How is it possible to design two heterogeneous electrode in vnl2008.10

« on: August 18, 2009, 12:49 »

Have a look at the tutorial regarding convergence under Publications>Tutorials on our website. Also, there are several discussions on the Forum.