Graphene-TwoProbe system

[bjnagare]

My system of two probe (Graphene-Graphene-Graphene) is converging well with (1,1,50) kpoints with msrh cutoff of 150Ry and single zeta polarized. The same system is not converging with (10,1,100) kpoints. Kindly suggest some guidance.

Thank you

[zh]

You may try to increase gradually the size of k-point mesh and do a restart calculation from a previous converged scf calculation with smaller k-point mesh.

[Anders Blom]

Is it pure 2D graphene in the electrodes? In that case you will want to take care to include the K point in the k-point sampling. Try 9 k-points instead, or some other multiple of 3 (although it's not always the K point is included anyway).

[bjnagare]

Dear Sir,

Yes. It is pure 2D Graphene.

But I haven't understood the concept of K point sampling with multiple of 3.

Thank you

Nagare

[zh]

The K point mentioned here  is ".333333333333333, .333333333333333, .000000000000000" in lattice coordinate format. This is due to the peculiar band structure of graphene, i.e., the 2 bands near the Fermi level due to the [tex]\pi[/tex] and [tex]\pi^{*}[/tex] states are crossing around the K point. For example, pls see here:
http://www.iue.tuwien.ac.at/phd/pourfath/node18.html

[bjnagare]

Dear Sir,

Thank you very much for your helpful suggestion.

Regards

Nagare

[fangyongxinxi]

Dear
It seems that you are not satisfied with the pure 2D graphene in the electrodes. What is your seggestion about setting electrodes for graphene if I want to do this job in ATK 2008 ?
In ATK-SE manule, eamples about big system is little, hopping to see more .