[DFTB-Plus-User] Failed geometry optimisation for 5 Au atom cluster

[Tiem Leong Yoon]

We have constructed a Slater-Koster file for gold(Au) nanocluster and run on
dftb+. The Slater- Koster information is the courtesy of Prof. Koskinen,
author of the paper "Density-functional based tigh-binding study of small
gold cluster, P. Koskinen et al 2006, New J. Phys. 8, 9.

We found that geometry optimization converged for 5 atoms of gold but when
run with 6 atoms, the geometry would not converge even after 10000 geometry
step.

For your information, the "OrbitalPotential" already added in the input file
and those values are the suggestion from Prof. Koskinen.

Anything we might have overlooked in the input file?

Below is the input file.


Geometry = GenFormat {
6   C
Au
1    1     3.0         0.0      0.0
2    1     -3.0        0.0      0.0
3    1     0.0         3.0      0.0
4    1     0.0        -3.0      0.0
5    1     0.01       0.02    3.0
6    1     0.03       0.02   -3.01
}

Driver = ConjugateGradient {
  MovedAtoms = Range { 1 6 }
  MaxForceComponent = 1.0e-4
  MaxSteps = 10000
  OutputPrefix = "geom.out"
  Constraints = {}
}

Hamiltonian = DFTB {
  SCC = Yes
  SCCTolerance = 1.0e-5
  MaxSCCIterations = 1000
  Mixer = Broyden {
    MixingParameter = 0.2
  }
  SlaterKosterFiles = {
    Au-Au = "Au-Au.skf"
  }
  MaxAngularMomentum = {
    Au = "d"
  }
  Charge = 0.0
  SpinPolarisation = {}
  Filling = Fermi {
    Temperature [Kelvin] = 0.0
  }

Eigensolver = RelativelyRobust {}
OrbitalPotential = FLL {
 Implementation = "on-site"
 LConstants = {
  Au = {0.25 0.25 0.25 }
  }
}
}


Options = {}
ParserOptions = {
  ParserVersion = 3
}
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