QuantumATK Forum

QuantumATK => General Questions and Answers => Topic started by: berna on February 9, 2018, 08:29

Title: Cell structures of nanosheets
Post by: berna on February 9, 2018, 08:29

Hi. I noticed that your graphene or MoS₂ nanosheet samples did not convert hexagonal lattice. I think they should be convert to their original or naturel lattice type. Could you explain why did not you conver them to hexagonal lattice?
Thank you.

Title: Re: Cell structures of nanosheets
Post by: Petr Khomyakov on February 9, 2018, 15:31

Please could you clarify your question? A nanosheet is no longer a crystal, meaning that no Bravais lattice can be assigned to it. So, what do you then mean by "they should be converted to their natural lattice type". Also the shape of nanosheets is not uniquely defined. One may choose some shape related to a particular experimental sample or propose a nanosheet with some unique properties, hoping that it can be realized in real-life experiment.  So, it is pretty much your choice.

Title: Re: Cell structures of nanosheets
Post by: Anders Blom on February 20, 2018, 08:16

I think I understood the main point of the question. It is correct we choose to represent these supercells using the UnitCell class instead of the Hexagonal Bravais lattice class in Python. Partly this is because a lot of times the purpose for creating such a supercell is to perform transport calculations, and then it's a lot more useful to have a consistent rule how the Z axis is aligned. Second, it might be confusing if it's a Hexagonal cell and someone computes the band structure and sees a lot of folded bands - in this case it is better the user is herself or himself responsible to convert the structure to Hexagonal (easy, usually).