Messages

1

General Questions and Answers / Re: the difference between graphene junction and nanoribbon with two electrodes

« on: November 17, 2011, 08:49 »

Thanks Anders.
problem solved.
But it has nothing to do with temperature.

2

General Questions and Answers / Re: the difference between graphene junction and nanoribbon with two electrodes

« on: November 16, 2011, 15:18 »

Yes.
And the electrode temperature is 5 K. But I think it does not matter.

3

General Questions and Answers / Re: the difference between graphene junction and nanoribbon with two electrodes

« on: November 16, 2011, 15:07 »

No.
I mean the conductance does not change with the gate voltage.
The gate volttage ranges from -10V to 10 V, but the conductance is the same.

4

General Questions and Answers / Re: the difference between graphene junction and nanoribbon with two electrodes

« on: November 16, 2011, 14:34 »

Dear Anders Blom

I use extended Huckel to analyze the relationship of conductance and gate voltage.
I set the k-points in the C direction is 300, the rest parameters are the same as the Graphene Device tutorial. But it turns out the conductance does change at all.

So which result is correct, mine or the tutorial?
More k points leads to better accuracy, right?

5

General Questions and Answers / Re: the difference between graphene junction and nanoribbon with two electrodes

« on: November 15, 2011, 14:28 »

Thanks again

6

General Questions and Answers / Re: the difference between graphene junction and nanoribbon with two electrodes

« on: November 15, 2011, 14:12 »

Thank you for your quick and detailed reply.
So you mean graphene junction and nanoribbon with two electrodes are totally different structures.
About Huckel, can it handle doping or defects? And it seems that the mesh cut-off and K-points of Huckel are much smaller than that of DFT. Dose it mean by Huckel we can get an accurate result with fewer K-points?

7

General Questions and Answers / the difference between graphene junction and nanoribbon with two electrodes

« on: November 15, 2011, 12:34 »

The tutorial of graphene device uses a graphene junction(z-a-z) and extended huckel to analyze the electric characteristics.  Is there any difference between nanoribbon (from custom) with electrodes and the graphene junction(from custom)?
And the best method to study graphene bandstructure is extended huckel http://quantumwise.com/forum/index.php?topic=1069.0 
How about electric characteristics?
If huckel is best, why do most papers I read use ATK-DFT?
Thank you

8

General Questions and Answers / Re: Convergence problem in 11.8b1

« on: November 3, 2011, 14:08 »

expired on my computer

9

General Questions and Answers / Re: The effect of bias on transport property?

« on: November 2, 2011, 02:46 »

But can we get the DOS and bandstructure of electrodes by ATK?

10

General Questions and Answers / Re: How to set the spins of the right and left electrode atoms respectively?

« on: October 28, 2011, 04:28 »

Actually, I'm confused too.
What is the difference between electrode and electrode copy and how can I change one without affecting another?

11

General Questions and Answers / what is multigrid residual?

« on: October 21, 2011, 08:51 »

Running 11.8, I encounter a warning:
################################################################################
# WARNING                                                                      #
#                                                                              #
# The computed multigrid residual is greater than the required accuracy.       #
#                                                                              #
# Computed residual :   8.88278e-006                                            #
# Required accuracy :   1.00000e-009                                            #
#                                                                              #
################################################################################

What is the multigrid residual and how to set it?
Nothing happened when I run the same program by 11.2.
 

12

General Questions and Answers / Re: optical properties of nanoribbon

« on: October 13, 2011, 16:35 »

Thank you for this detailed reply

13

General Questions and Answers / Re: optical properties of nanoribbon

« on: October 13, 2011, 13:15 »

Yes, I saw that. But the material is directly from Database.
If I design some structure by the Builder, can 11.8 calculate this?
And I find the the absorption of graphene and graphene sheet are totally diffenrent.

14

General Questions and Answers / optical properties of nanoribbon

« on: October 12, 2011, 16:06 »

Can ATK 11.8 calculate the optical absorption of graphene sheet or nanoribbon?