Stone-Wales defects - that is, a 90 degree bond rotation which turns two neighboring hexagons into a double pentagon/heptagon pair - are naturally occurring in nanotubes (and graphene), and can have a strong influence on the electronic structure. It is therefore of great relevance to model defect structures to understand their importance on e.g. transport properties.

In this tutorial you will learn how to create a Stones-Wales defect in a nanotube, and results will be shown that indicate the influence the defect can have on the transmission spectrum.

The trick is to create the Stone-Wales defect in graphene, which is a planar structure and so it's much easier to define the proper bond rotation,, and then roll the structure into a nanotube.

Creating a capped nanotube is an easy task to perform using the Builder, but it's perhaps not entirely obvious how to do it. This tutorial teaches you the necessary steps!

In some multilayer graphene structures, the layers are rotated with respect to each other as a result of the growth process. This can often be seen as a Moiré pattern in experimental pictures. Setting up such structures for simulations requires a little bit of work - but not too much, as you can see below.

For a concrete example, let us consider a case from Phys. Rev. B 78, 125406 (2008), where the top layer in a 3-layer stack is rotated 21.8 degrees. The challenge is to set up a commensurate supercell.

Building a carbon nanotube in VNL is more or less trivial, since there is a dedicated plugin for it. That tool is also able to create B-N tubes, as well as multiwall structures.

But what if you want something more complicated, like a MoS₂ nanotube, like those studied in G. Seifert et al., Phys. Rev. Lett. 85, 146 (2000)? A logical approach seems to be to first make a hexagonal sheet, just like graphene, and then wrap it into the shape of a tube. Indeed, such a "tube wrapper" plugin has been developed, and in this tutorial you will use it to learn how to make MoS₂ and other metal sulfide TS₂ nanotubes (cf. A. Kuc et al., Phys. Rev. B 83, 245213 (2011)).

This quick tutorial shows you how to make a small defect in graphene, viz. a hole, and passivate it with hydrogen atoms to saturate all the bonds

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ATK can also handle heterogeneous systems, where the two electrodes are not the same, as demonstrated in K. Stokbro et al., PRB 85, 165442 (2012). Here you will learn how to build a similar system.

In this tutorial you will learn how to use the Builder in VNL to construct one of the most famous molecular junctions – a dithiole-benzene, DTB (sometimes also known as benzene-dithiole, BDT) embedded between two gold (111) surfaces.

This tutorial will show you how to build a complex interface, using the Builder in VNL 12.2 or later. As example, the β-Si₃N₄(0001)/Si(111) geometry as studied in detail in M. Yang et al., J. Appl. Phys. 105, 024108 (2009) will be used. As stated in the article, an earlier model for the crystalline interface of β-
Si₃N₄
(0001)/Si
(111) was proposed by Zhao and Bachlechner, but that model contained dangling bonds, which is not consistent with experimental findings. The interface you will build here has all bonds saturated.

Below are images of systems that were all built with the Builder in VNL, in no case involving more than 10 minutes of work for an experienced user.

More detailed instructions will come soon!

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and more!