Yambo Community Forum

Dear Davide,
it is running without any error!

Thanks for the help.

Dear Fabio,
this is to inform you that a new release of yambo containing many bug fixes, including the one you faced, has been released.
For the moment the new version is in the svn repository only, in the next day we will also prepare the tarball and the release note.
Please note this is still a devel version, and we will be very glad if you could report us any problem you encounter.

Best,

Daniele

Dear all,

I'm not sure if this is a problem, but as you know from previous problems, i'am doing some test calculations with graphene 2D. I am continuing post in this topic because it is related to ypp band interpolation.

Something that is confusing me is that when i use in nscf a 8X8X1 or a 16X16X1 KPOINTS grid, the yambo doesn't consider the graphene as metal system in it's initialization. But when i use 12X12X1 or 24X24X1 it gives me the warning of the metallic system. I think that this has something to do with the Dirac point not be included in 8X8X1 and 16X16x1 kgrid, but i'm not sure.

The main problem is that if i choose 8X8X1 or 16X16X1, and do a yambo COHSEX calculation, there is a open gap in the interpolated band. This does not happen with 12X12X1 where we can see the Dirac cone (still testing in 24X24X1).

How can i solve this problem in order to have the Dirac point in 8X8X1 or 16X16X1 in the band interpolation?

Thanks,

Fabio

Dear Fabio,
yambo reads what the quantum espresso provides. It is not an easy task to have the cone features when you do not include the cuspi. If you increase the electronic temperature: you can do it in input file, yambo will see the system as a metal but I doubt the interpolation can produce the Dirac cone anyway, being the Dirac point a cusp, in order to have it I think you need to include it in your sampling.
Best,
Daniele

Dear Fabio,
I fear you cannot have a good interpolation without the Dirac point included in your database.

Yambo decides if the system is a metal or not based on the occupations at the kpoints which you have computed.

Also the interpolation is based on smooth functions and whatever you try, if the Dirac point is not included in the starting mesh, the natural outcome will be to open a gap.

D.

Dear Daniele and David,

thanks for your answers.

By the way, in the ypp -k k tutorial in website, the file containing the dielectric constant is SAVE/ndb.pp. What is the name of the file in the new version?

Thanks,

Fabio

Dear Fabio,
the name of the databases are not changed at all.
Best,
Daniele

Dear Daniele,

Sorry for this naive question, but what should i do to include the dielectric constant file in SAVE folder? I thought that doing a COHSEX or PPA calculation was enough to get the ndb.pp in SAVE folder.

Thanks,

Fabio

Dear Fabio,
as you said, a PPA calculations will produce an ndb.pp database. COHSEX approximation is a static approximation so the static screening is needed (em1s). If you do not have the database or something went wrong and the calculations was not properly finished or you are using the -J dirname option when running yambo. In the latter case the databases containing the screening will be in the dirname directory.

Best,
Daniele

Dear Daniele,

yes i'm using -J dirname option, and ndb.pp it's there.

Thanks,

Fabio