Edge Functionalization of Graphene Nanoribbons

[sadegh]

Hello All,

I want to investigate F-, Br- , and Cl-, terminated graphene nanoribbons. As you may know ,and also you can find in the following references, the most stable geometry for halogen – terminated graphene nanoribbons has rippled in the edges. My question is that in ATK if one wants to consider all configurations (planar or edge rippled with all possibilities in order to find the most stable configuration, I mean, in a unit cell, one edge up and one edge down….), how should we apply ripples to edges of the nanoribbons before optimization step? I want to know how I can get their results using ATK?

I would really appreciate it if one could shed some light on this question.


- First-principles study of edge-modified armchair graphene nanoribbons:

http://scitation.aip.org/content/aip/journal/jap/113/18/10.1063/1.4804657

- Ripple edge engineering of graphene nanoribbons:

http://journals.aps.org/prb/abstract/10.1103/PhysRevB.84.134110

[Umberto Martinez]

Most probably you will obtain the rippled structure by simply optimizing your structure due to steric repulsion.
Anyway, you can help the process and indeed speed it up by building a good initial structure, as you suggest.

Simply use the Move tool in the builder to rotate the dihedral angle of the selected termination.
See screenshot attached and the manual for usage instruction here http://quantumwise.com/documents/tutorials/latest/BuilderManual/index.html/chap.move.html#sect1.move.dihedral

[sadegh]

Dear Martinez,

Thanks for your quick response. I will try the Move Tool.

Just a point, I expected, unlike flat edges of hydrogenated graphene, halogens cause armchair edges to form out of plane distorted ripples due to steric repulsion. But, with simply changing hydrogen atoms to for example F atom, I got a completely flat structure!
I used: DFT method, Exchange correlation: LDA-PZ, basis-set: Double Zeta P, k-point: 1*1*12
 max Force: 0.005 ev/A, max stress: 0.05 ev/A3, without applying constraints.

Do I need to bring atoms close together in order to overlapping of their electron clouds?

   

[zh]

To get the distorted edges, you have to use a large supercell, which contains at least two periodic lengths. Besides this, you may give a small perturbation to the initial positions (particularly for the z coordinates, if the ribbon is placed in the xy plane) of atoms, i.e., the z coordinates of the edge atoms are changed to be slightly different to those of the atoms in the middle region of ribbon.