[DFTB-Plus-User] DFTB+: geom.opt periodic 2D graphene

[NURIA AGUILAR CUESTA]

To whom it may concern,

this is the massage I would like to post to all the list members:

"Hello everyone,

my name is Nuria and a I'm a PhD student in computational chemistry.
I'm kinda new to DFTB+ calculations.
I am trying to run a geometry optimization on a periodic 2D graphene with variable cell. I tried an isotropic calculation as I do not want the bond distances nor the angles between C atoms to change, only as if it's read on the manual: 'Isotropic If optimising the lattice, allow only uniform scaling of the unit cell.'
Despite that, the bond lengths and angles keep changing and the periodic boundary condition would not replicate the graphene periodic structure correctly creating interfaces large enough to consider the structure as a graphene sheet.

I tried to run a non variable cell geometry optimization to check the rest of the input and the job ended correctly.

The graphene structure has 720 C atoms and the PBC for that is shown below.
The code I used to run the calculation was the following:

   0.00000000000E+00   0.00000000000E+00   0.00000000000E+00
   0.44529500000E+02   0.00000000000E+00   0.00000000000E+00
   0.00000000000E+00   0.42871200000E+02   0.00000000000E+00
   0.00000000000E+00   0.00000000000E+00   0.30000000000E+02
}

Driver = GeometryOptimization {
  Optimizer = SteepestDescent {
   ScalingFactor = 1.0
  }
  LatticeOpt = Yes
  Isotropic = Yes
  MaxSteps = 500
  OutputPrefix = "geom.out"
  AppendGeometries = Yes
}

I would greatly appreciate any help to run the calculation properly.
Thank you all for your help.

Kind regards,
Nuria

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.zfn.uni-bremen.de/pipermail/dftb-plus-user/attachments/20230814/e9a9f889/attachment.htm>