Hello,
I apologize if this is not the correct category.
I am performing DFTB+ calculations for the adsorption of an organic corrosion inhibitor on an Fe slab using the PTBP parameter set. The Fe surface model contains 320 atoms (8×8×5), and only 2 the upper layers together with the molecule are relaxed.
My main concern is the reliability of the adsorption energies obtained from the calculation,
Currently, I am using:
Driver = GeometryOptimization {
MovedAtoms = 129:-1
MaxSteps = 1000
AppendGeometries = Yes
LatticeOpt = No
}
Hamiltonian = DFTB {
SCC = Yes
ShellResolvedSCC = Yes
MaxSCCIterations =1000
SCCTolerance = 1e-8
ConvergentSCCOnly = No
Mixer = Broyden { MixingParameter = 0.08 }
MaxAngularMomentum {
Fe = “d”
H = “s”
O = “p”
C = “p”
}
Solver = DivideAndConquer{}
Charge = 0.0
SpinPolarisation = Collinear {
UnpairedElectrons = 0
RelaxTotalSpin=Yes
}
SpinConstants {
Fe {
-0.016 -0.012 -0.003
-0.012 -0.029 -0.001
-0.003 -0.001 -0.015
}
C {
-0.031 -0.025
-0.025 -0.023
}
O {
-0.035 -0.030
-0.030 -0.028
}
H {
-0.072
}
}
ReadInitialCharges = No
Dispersion = LennardJones {
Parameters = UFFParameters {}
}
SlaterKosterFiles = Type2FileNames {
Prefix = “/home/ptbp/”
Separator = “-”
Suffix = “.skf”
LowerCaseTypeName = No
}
KPointsAndWeights = SupercellFolding {
1 0 0
0 1 0
0 0 1
0.0 0.0 0.0
}
Filling = Fermi {
Temperature [Kelvin] = 300.000
}
Parallel = {
UseOmpThreads = Yes
}
The calculation converges and produces adsorption energies of around -10 eV, but I’m sure these values are impossible.
I would greatly appreciate any recommendations for obtaining more reliable adsorption energies for Fe-organic systems using DFTB+.
Thank you very much.