silicone Quantum Espresso.in related query

[anibose3]

Dear Experts,
I have created the unit cell of silicine by altering the unit cell of Graphene as suggest by the method  proposed in VNL ATK tutorial.But unfortunately I don't find the hexagonal point group symmetry in relax.out file of silicine.But for Grapheme I get the correct symmetry (D6h) and for silicene it is the same.Is it a major drawback of VNL ? No direct structure of silicene is not provided VNL.How can I resolve the issue?

Thanks and regards,
Anindya Bose
Research Fellow,
IIIT Allahabad

[Petr Khomyakov]

Please explain what you did in a step-by-step manner, and then point out where the issue appears.

[anibose3]

I Started by adding graphene  from the Database to the Stash.
Change the two atoms to Si by selecting them and use the Periodic Table tool change_element .
The lattice constant of silicene is not the same as for graphene, I set it to 3.8 Å, otherwise the forces will be too large in the beginning of the optimization. Also increase the C lattice constant to 20 Å (in both cases making sure to keep the fractional coordinates fixed). Therefore the structure was taken in centre by using coordinate tool.Later I export this structure by espresso.in format and processed it.But relax.out doesn't show the correct point group symmetry.

Thanks and regards,
Anindya Bose

[anibose3]

I forget to mention one more thing , I rattled the structure too to create buckling.However nothing rectified the point group symmetry error.Please suggest me what to do?

Thanks and regards,
Anindya Bose

[Petr Khomyakov]

I do not understand why you assume that the symmetry of the system should not change after buckling. Could you also post your python script with the buckled structure.

[anibose3]

Dear Mr  Petr Khomyakov,
I completely understand what you are trying to mention.In that case I have just two queries
1.Is there any ready made silicene structure in quantumwise library like Graphene with which I can directly start my calculation?
2.If I do not buckle the structure ,just replace the Graphene atoms with silicon.In that case will the hexagonal symmetry be unaltered?
I am looking for a solution.

Thanks and regards,
Anindya Bose

[Petr Khomyakov]

Knowing the symmetry of silicene, you must be able to build the structure using the Crystal Builder, see https://docs.quantumwise.com/tutorials/crystal_builder/crystal_builder.html.

[Anders Blom]

Did you read https://docs.quantumwise.com/tutorials/opening_a_band_gap/opening_a_band_gap.html#silicene?