Slater-Koster and Tight Binding parameters

[Hesam]

Is it possible to extract the Slater-Koster Tight Binding (TB) parameters for a material using ATK. For example I was wondering if I can obtain tight binding parameters for MoS2 (mono layer and multi layer). Is it possible? Are you using semi empirical TB in case of Slater-koster calculator?

[kstokbro]

In the scripter select script details = "show defaults" and save the script. It now has all the details,

[Hesam]

Thanks, where is this option? I couldn't find it.

[Hesam]

I found that option and used it but there is nothing in the output log about the Tight Binding parameters (or Slater-Koster table). How I can access those parameters if they are stored somewhere?

[Hesam]

Maybe I can't see the SK parameters since it is DFTB parameters?! I want to see the parameters like onsite elements (i.e Es, Ep) and coupling terms (i.e Vsp_sigma).

[Anders Blom]

There is some confusion here regarding whether you mean the SK parameters used in the calculation, or how to fit your own SK parameters from a DFT calculation.

The question was answered for the former case - how to see which values are used in the calculation for a chosen parameter set. In this case, in the Script Generator select "Show defaults" and send the script to the Editor.

If you want to fit your own parameters, there is no magic way to just run a calculation and extract a full set of Slater-Koster parameters. We are working on some more automated ways that may or may not always work, but for now and in general, you have to assume some parameters and do the calculation, compare to DFT or experiment, and use some general fitting routine (genetic algorithm, Nelder-Mead, etc), to adjust the parameters and try new values etc, in a systematic fashion. There are lots of papers on how to fit parameters - it's kind of an art more than anything else.

[Hesam]

Many thanks for your reply. I want to see the Slater-Koster parameters used in ATK not to fit (despite it would be nice). My problem is that when I save the python file with the "script details = show defaults" then I just see something like the following not a real parameter set for MoS2. Could you please explain how I can get the real parameter set (E_s, E_p, ...).

# -------------------------------------------------------------
# Calculator
# -------------------------------------------------------------
#----------------------------------------
# Basis Set
#----------------------------------------
basis_set = DFTBDirectory("cp2k/nonscc/")

#----------------------------------------
# Pair Potentials
#----------------------------------------
pair_potentials = DFTBDirectory("cp2k/nonscc/")

numerical_accuracy_parameters = NumericalAccuracyParameters(
    interaction_max_range=10.0*Angstrom,
    electron_temperature=300.0*Kelvin,
    reciprocal_energy_cutoff=1250.0*Hartree,
    number_of_reciprocal_points=1024,
    radial_step_size=0.01*Angstrom,
    density_cutoff=1e-06,
    k_point_sampling=(15, 15, 10),
    density_mesh_cutoff=10.0*Hartree,
    )

[Anders Blom]

I see. There is no simple way to just print the tables, since we have no corresponding input format for DFTB parameters. All parameters are specified in the "skf" files, so the quickest answer is to look in the files (Mo-Mo.skf etc) in atkpython/share/tightbinding/cp2k in the ATK installation.

[Anders Blom]

Just as a friendly note: if your last message had been the original post, you would have gotten your answer much easier and quicker. The more precise a question is, the easier it is to answer, without speculation.