PTBP_Lab

Density Functional Tight-Binding Parameterization: Periodic Table Baseline Parameter Set (PTBP)

PTBP Logo

PTBP is a periodic-table-wide DFTB parameter set covering 75 elements (H–Th), designed to give a robust and systematically improvable baseline rather than the highest-possible accuracy on any single system. It is the low-fidelity baseline used by PTBPlus, and the parameter files can be downloaded from the SKF File Download page.

Methodology in brief

Each elemental parameter set is fitted against energy–volume curves computed at the PBE level for the most relevant crystal phases of the element. To avoid overfitting to a single phase, the loss function is averaged over multiple phases using Boltzmann-factor weights:

\[ p_i = \frac{e^{-E_i / k_\mathrm{B} T}}{\sum_j e^{-E_j / k_\mathrm{B} T}} \]

Configurations with \(p_i > 0.1\) are included in the fit; less stable phases are dropped. For noble gases, only energies (no forces) are used.

Two electronic confinement parameters are tuned per element:

  • \(r_\mathrm{w}^{0}\) — wavefunction confinement radius

  • \(r_\mathrm{d}^{0}\) — electron-density confinement radius

The repulsive part is then fitted on top. Performance is reported as the relative volume error \(\mu_V\) (mean across the included phases).

Overall Performance of All Elements

The interactive periodic table below summarizes the fit quality for each element. Hover an element to view its energy-vs-distance fit curve; the marker color encodes the relative volume error band:

μV < 3% μV < 5% μV < 10% Noble gas (energies only)

Hover for a quick hint · click an element to load its fit curve and download SKFs.

See also

  • PTBPlus — multi-fidelity transfer learning built on top of PTBP

  • SKF File Download — generate and download SKF files for any subset of elements

Citation

M. Cui, K. Reuter, J. T. Margraf. Periodic Table Baseline Parameter Set for Density Functional Tight-Binding. J. Chem. Theory Comput. 20, 5276–5290 (2024). doi:10.1021/acs.jctc.4c00228