a spin problem

[renren123123]

recently, I want to calculate something on graphene ribbons, and we know we best consider its spin effect,  I using ATK 2008.02 trail, if we add some spin value
to corresponding atoms on its option process wihtin VNL2008.02,  In the process of
option, its spin value will vary, How can I know its spin value of every atom in my system ?  Thank you very much!!!

[kstokbro]

Hi renren,
Can you post your script and the output then it is easier to see what is the problem? It could be that the system did not converge properly.

You can have different types of electrodes, but sometimes convergence can be delicate.

I also recommend upgrading to the latest version, ATK2008.10.0 it is much improved, both faster and more stable.

Regards,
kurt

[Nordland]

Hej Renren123123.

I am not sure exactly what you mean by your question, but I will try to answer it anyway.

When dealing with periodic systems (and two-probes) you can set the initial spin for
the system atom by atom. This is qualified guess, however if you don't have any idea what the initial spin
should be, you set the initial scaled spin to 1 for all the atoms.

In VNL under the option "initial scaled spin", if you enter a single value there, it will use this value for all the atoms
in the system, and hence you can just enter 1 here at it should work.
The results will not depend on this value since it is just a qualified guess, but you will perhaps have longer calculation time
if the self-consistent density is far away from your guess.

I hope this answered your question.

[renren123123]

Thank you for your help !

[Anders Blom]

There is a tutorial on the web site (http://quantumwise.com/publications/tutorials) on the topic of graphene nanoribbons that you might find useful.

Regarding the original question, when you refer to the "spin value of every atom in my system", do you mean the resulting spin polarization of each atom produced by the self-consistent calculation, or is this still a matter of input?

For output, you should look at the Mulliken populations. For input, I recommend looking in the manual under electronDensityParameters()

[Nordland]

Wow! Nice tutorial!