pygfn0_torch
============

This project is distributed under GNU GPL-3.0-or-later. See LICENSE.

This source distribution does not include fitted GFN0-xTB parameter files,
fitted/global GFN0 scalar defaults, SRB support tables generated from upstream
sources, or generated D4 support TSVs. Users must provide those local inputs
under terms they have verified for their own workflows.

STO/Gaussian expansion support
------------------------------

This project includes STO/Gaussian expansion support used to evaluate contracted
Gaussian surrogate integrals for the overlap, dipole, Cartesian multipole, and
point-charge embedding paths. STO-NG means a Slater-type orbital represented by
N Gaussian primitives. This support is distinct from the externally supplied
GFN0-xTB fitted parameter file. Element coverage is determined by the
combination of the user-supplied parameter file, the implemented basis
construction, and validated tests; it should not be inferred from the embedded
STO/Gaussian tables alone.

Parts of the STO/Gaussian expansion data and related overlap-path
implementation logic are derived in part from:

  pprcht/gfn0
  file: src/slater_module.f90
  release tag: v0.1
  release URL: https://github.com/pprcht/gfn0/releases/tag/v0.1
  raw file URL: https://raw.githubusercontent.com/pprcht/gfn0/v0.1/src/slater_module.f90
  commit-level cross-check: 9cc774e
  note: the v0.1 source file and the 9cc774e file are byte-identical in the
        reviewed provenance check

The referenced source file is distributed under GNU LGPL-3.0-or-later and
attributes the original unmodified source to the xtb project under GNU
LGPL-3.0.

Copyright notices preserved from the referenced source context:

  Copyright (C) 2022-2023 Philipp Pracht
  Original unmodified source from xtb:
  Copyright (C) 2019-2020 Sebastian Ehlert

The derived STO/Gaussian implementation is redistributed as part of this
GPL-covered work. The original copyright and license notices are preserved.

Scientific reference:

  R. F. Stewart, "Small Gaussian Expansions of Slater-Type Orbitals",
  J. Chem. Phys. 52, 431-438 (1970), DOI: 10.1063/1.1672702.

Internal kernel-schema compatibility scalars
-------------------------------------------
A small number of scalar fields may be generated locally when translating a
complete user-supplied `param_gfn0-xtb.txt` file into the current C++ tensor
layout. These fields are not a bundled fitted GFN0-xTB parameter table and do
not remove the requirement to supply the external parameter file.

Their provenance is recorded explicitly in the source comments, in the same
spirit as the STO/Gaussian orbital-expansion provenance above. The compatibility
values follow the standalone Fortran GFN0-xTB implementation conventions in
`gfn0_param.f90`, `gfn0_types.f90`, and `eeq_module.F90`: f-channel shell
entries, Hamiltonian EN-scale construction, pair-parameter scaling for d-block
and coinage-metal pairs, the default dispersion `s6` field, and the EEQ hardness
term without an additional multiplier.
