[DFTB-Plus-User] Deuterium mass assigned to hydrogen

[Bálint Aradi]

Dear Daniele Veclani,

it should in theory work. With the following input, I can run md without 
any problems with DFTB+ 22.1:

Geometry = GenFormat {
3  C
  H
      1    1    0.00000000000E+00   0.00000000000E+00   0.00000000000E+00
      2    1    0.80000000000E+00   0.00000000000E+00   0.00000000000E+00
      3    1    0.20000000000E+00   0.60000000000E+00   0.00000000000E+00
}

Driver = VelocityVerlet {
   Steps = 100
   TimeStep [Femtosecond] = 0.10
   Thermostat = None {
     InitialTemperature [Kelvin] = 273.15
   }
   Masses {
     Mass {
       Atoms = "H"
       MassPerAtom [amu] = 2.0
     }
   }
}

Hamiltonian = DFTB {
   SCC = Yes
   MaxAngularMomentum = {
     H = "s"
   }
   SlaterKosterFiles = {
     H-H = "H-H.skf"
   }
}


Best regards,

Bálint

On 25.11.22 14:47, daniele.veclani at isof.cnr.it wrote:
> Dear users,
> 
> I am performing an MD simulation with DFTB+ 21.2 of the water 
> interaction with a surface. The level of theory is SCC-DFTB and the 
> timestep 0.5 fs, NVT 300 K with Nose-Hoover, Matsci + mio S-K 
> parameters. I was wondering if with this method is recommended to assign 
> the deuterium mass to hydrogen, as usually happens for ab-initio MD at 
> other levels of theory (e.g. BOMD, CPMD) because of the high 
> vibrational frequency of the H-bonds. If so, I can not figure out how 
> this can be specified in the dftb_in.hsd input. I tried both the ways 
> exposed in the manual, i.e.:
> 
> Masses {
> Mass {
> Atoms = 1:2
> MassPerAtom [amu] = 2.0
> }
> 
> }
> 
> and
> 
> Masses {
> Mass {
> Atoms = H
> MassPerAtom [amu] = 2.0
> 
> }
> 
> }
> 
> even if the latter one seems limited to the MODES input, but I always 
> get an error message.
> 
> Any advice is appreciated.
> 
> Thank you in advance.
> 
> Best,
> 
> Daniele Veclani.
> 
> 
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-- 
Dr. Bálint Aradi
Bremen Center for Computational Materials Science, University of Bremen
http://www.bccms.uni-bremen.de/cms/people/b-aradi/


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