Topics

1

General Questions and Answers / Can van der Waals interaction included in the calculation?

« on: January 11, 2012, 17:50 »

As van der waals force is dominant in layer graphene system? Dose ATK provide any routine to include van der waals interaction in the calculation? How much will the exclusion of van der waals interaction impact the accuracy of the result?

2

General Questions and Answers / A question about three terminal device

« on: October 7, 2011, 13:01 »

If I construct bulk device with three terminal, like the model in the tutorial" Graphene junction device", which the gate controlling region is finite nanoribbon, so my question is if I construct the three terminal device like the attachment, in the calculation will the gate region be treated also as infinite?

3

General Questions and Answers / Disagreement between the result I got and the result in publication

« on: September 8, 2011, 12:34 »

Why the optimized interlayer distance of bi-layer Graphene is 3.08 Angstrom, but the value in other publication is around 3.3 Angstrom(reference for http://apl.aip.org/resource/1/applab/v92/i22/p223106_s1 also using ATK), is there anything wrong with my calculation ?

4

Scripts, Tutorials and Applications / Puzzle about the I-V characteristics of bilayer graphene compared with monolayer

« on: September 3, 2011, 09:13 »

I have done the calculation of bilayer gaphene and monolayer graphene, but I found that the current of bilayer graphene is larger than twice of monolayer graphene when the applied bias is low.(see the attachment)

This is strange because I think in any case the conductivity should be lower than parallel of two monolayer graphene because of interlayer scattering in bilayer system.

So I doubt the accuracy of my calculation, the script is attached, I beg help for checking anything wrong with my setting or is there any question with my assumption for I haven't seen any reference about such phenomenon.

5

General Questions and Answers / Negative current under positive bias

« on: August 1, 2011, 03:11 »

When I set the right electrode negative voltage(like -0.2, -0.4,-0.6), I got negative currents, but when the negative voltage change to -0.8, -1.0, the current is positive. What's wrong? Dose the phenomenon make any sense?

6

General Questions and Answers / how to calculate working function

« on: July 17, 2011, 02:58 »

Can ATK calculate working function of a certain material?

7

General Questions and Answers / caculation of bloch state

« on: May 23, 2011, 18:46 »

When I calculate the bloch state of zigzag graphene nanoribbon using LDA, I found there is no item of 'none' for spin panel as in the tutorials. what is the problam?
And after I calculated the one spin bloch state of the lowest conduction band at Z, I found the one spin also localized on the edge of ribbon, just as the result using LSDA with the inital setting of edge spin polarizations. Is that right?

8

General Questions and Answers / A question about optimization

« on: May 15, 2011, 07:13 »

In the tutorial, the optimization is conducted under the sing zeta basis set to save the time, in practice I have try optimization of a bilayer system consisting of 150 atoms with the single zeta polarized basis set and find the process really time consuming. So is it acceptable to conduct the optimization using simple basis set while conducting analysis using more complex basis set? Optimization under simple basis set will influence the accuracy of the analysis result?

9

General Questions and Answers / A error

« on: May 15, 2011, 06:59 »

I was using ATK to calculate a system consisting of two layers of graphene nanoribbon with the interlayer distance is 8 Angstrom(the script of my model is attached) ,but as the calculation began there is error as follows, could anyone explain to me what is the problam?

                           |--------------------------------------------------|
Calculating Eigenvalues    :

** Back Engine Exception 541 : Diagonalization error, overlap matrix not positive definite, try to increase interaction_max_range
** Location : mathutils.cpp:1123


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