Nanopowder and Nanoparticle

[Inaoton]

Hello Sir,
                           How can i build the structure of nanoparticle in ATK?
And also nanopowder being agglomerates of ultrafine particles, how can i construct the structure of Nanopowder using Builder?

[Daniele Stradi]

To construct a nanoparticle of an arbitrary material, you can use the  Wulff Constructor plugin in the Builder.

[Inaoton]

Thank you.
And if i want to build nanopowder which is polycrystalline, what builder option should i use?

[Inaoton]

And also when i use wulff constructor, the configuration changes to a molecule. Why is it so?
I want to calculate the bandstructure.

[Ulrik G. Vej-Hansen]

What do you mean by nanopowder? A collection of different nanoparticles?
You can make polycrystalline alloy using the polycrystal builder, as described in this tutorial: https://docs.quantumwise.com/tutorials/creep_experiment_cu_polycrystal/creep_experiment_cu_polycrystal.html

The configuration is defined as molecule because a nanoparticle is a molecule, not a bulk. If you want to consider instead a periodical array of nanoparticles, you can change it to a bulk configuration by using the bottom in the toolbar at the top.

[Inaoton]

Thank you for your reply sir.
 The Wulff constructor needs surface energies of each plane. How can i determine these values ? can you please give me a reference

[Inaoton]

 The nanoparticle under study is polycrystalline. Should  I use polycrystal first and then the Wulff constructor or the vice-versa. which one is better?

[Ulrik G. Vej-Hansen]

For surface energies, there are various methods, but personally I prefer this one: https://arxiv.org/abs/cond-mat/9610046

The Wulff construction is not appropriate for making a polycrystalline nanoparticle. It uses the surface energies of specific facets to determine the sizes of those facets, and that will no longer be directly possible if the particle is polycrystalline. See also the Wikipedia page and the references therein: https://en.wikipedia.org/wiki/Wulff_construction

[Inaoton]

Is there any technique I can try to construct the polycrystalline  nanoparticle? Please share.

[Ulrik G. Vej-Hansen]

You can make a polycrystalline nanoparticle by first making a polycrystalline bulk and then cut out a particle. However, how to select the appropriate shape and size is not trivial, and depends on the your scientific model of your problem. In some cases the appropriate model might instead be a Boltzmann-weighted ensemble. Personally, I can suggest this paper, of which I am a co-author, but there are of course many, many others in the literature: http://www.sciencedirect.com/science/article/pii/S0021951711002673

[Inaoton]

Thank you very much sir