Topics

1

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

2

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.
 

3

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?