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

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

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.
