Topics

1

General Questions and Answers / a question about the conductance under finite biases

« on: December 14, 2010, 10:43 »

Dear everyone,
   In former post,"http://quantumwise.com/forum/index.php?topic=203.0",I guess the author obtained the conductance under bias in

Fig.3 by taking the value of transmission coefficient at E=0 according to each finite bias? Although,both fig.3 and fig.4 showed

the conductance variations under bias, they are far different. Which one is meanlingful?  Is it appropriate to consider the value

of transmission coefficient  at E=0 which is the average value of fermi levels of two electrodes?
    Any comment will be appreciated!!!

2

General Questions and Answers / one questions about the Graphene Nanoribbon Tutorial

« on: December 13, 2010, 10:21 »

Dear developers,

     In   Tutorial of Graphene Nanoribbon on this website "http://quantumwise.com/documents/tutorials/BasicGrapheneTutorial/XHTML/chap.zigzag_transport.html#chap.zigzag_transport.perfect_transmission", it said the enhanced transmission around the Fermi level was due to a peculiarity in the band structure of the zigzag ribbon. In my opinion, in such a one dimensional transport system, the electron would be transfered from the source electrode to the drain electrode only through the gamma(0,0,kz=0) point in the Brillouin zone and thus the peculiarity in the band structure of the zigzag ribbon far away from the gamma(0,0,kz=0) point along the kz line should be no use for electron transport and couldn't be related with the enhanced transmission around the Fermi level. But my opinion should be wrong. Do the kz points other than gamma(0,0,kz=0) point  also take part in the transport progress in such one  dimensional transport system?
   Thanks in advance!!!

3

General Questions and Answers / What's the relationship between the bloch state and tranmission eigenstate?

« on: July 2, 2010, 11:28 »

Dear all:

What's the relationship between the bloch state from the electrodes and tranmission eigenstate?
Any comments will be appreciated!

4

General Questions and Answers / A problem about how to set the K-point set for optimization

« on: March 16, 2010, 09:10 »

Dear everyone,

I want to relax the two-probe system like (Au wire)-(long DTB system)-(Au wire) by siesta, I don't know how to set the parameter k-sampling grid,I have a try of

 %block kgrid_Monkhorst_Pack
   1 0 0 0.0
   0 1 0 0.0
   0 0 60 0.5
%endblock kgrid_Monkhorst_Pack
but it is too slow to get the result ,so I want to know which number is enough for the k-sampling grid along z-direction?I think 60 is too big.

Thanks a lot in advance!