axtb: upstream work
===================

axtb is written in Rust. It reproduces the parameters and algorithms of the programs and
libraries below, parts of it are ports of their code, and it carries data taken from them.
Their source code, or for g-xTB 2.0.1 the released program, was read for that purpose. The
specifications in docs/ say, term by term, where each part comes from. Paths below are
relative to the repository, https://github.com/atomsforhumanity/axtb.

xtb (https://github.com/grimme-lab/xtb), LGPL-3.0-or-later
  GFN2-xTB as the xtb 6.8.0 and 6.7.1 programs compute it (conventions "xtb" and
  "xtb-6.7.1"), including the parameter and element tables of src/param; the ALPB/GBSA
  implicit solvation (src/solv, crates/solvation); GFN-FF (src/gfnff, crates/gfnff);
  the vibrational analysis and quasi-RRHO thermochemistry of `xtb --hess` and `xtb thermo`
  (the point-group detection is an independent implementation). The xtb side of the g-xTB
  2.0.1 build (https://github.com/thfroitzheim/xtb, branch gxtb) was read too.
  C. Bannwarth et al., WIREs Comput. Mol. Sci. 11, e1493 (2021), doi:10.1002/wcms.1493.
  GFN-FF: S. Spicher, S. Grimme, Angew. Chem. Int. Ed. 59, 15665 (2020),
  doi:10.1002/anie.202004239.

tblite (https://github.com/tblite/tblite), LGPL-3.0-or-later
  The GFN2-xTB parameters (xtb/gfn2.f90) and Slater-type orbital expansions (basis/slater.f90)
  in crates/axtb; GFN2-xTB as tblite 0.8.0 computes it (conventions "tblite"). The g-xTB
  branches of https://github.com/thfroitzheim/tblite were read for the g-xTB specifications.

dftd4 (https://github.com/dftd4/dftd4), LGPL-3.0-or-later
  The DFT-D4 model of dftd4 4.3.1 and its reference tables (src/dftd4/reference.inc,
  src/dftd4/data) in crates/d4; the revD4 tables that g-xTB shares with it.

simple-dftd3 (https://github.com/dftd3/simple-dftd3), LGPL-3.0-or-later
  Five test structures in tests/structures (tests/structures/README.md).

mctc-lib (https://github.com/grimme-lab/mctc-lib), Apache-2.0
  Element data (Pauling electronegativities, covalent and atomic radii) and the CODATA 2018
  constants of src/mctc in crates/axtb and crates/d4; the Angstrom-to-bohr factor of the
  programs that read structures through it.

multicharge (https://github.com/grimme-lab/multicharge), Apache-2.0
  The EEQ 2019 parameters (param/eeq2019.f90) in crates/axtb; the EEQ-BC 2025 model that
  g-xTB uses.

g-xTB (https://github.com/grimme-lab/g-xtb), GPL-3.0
  crates/gxtb/param holds the parameter files of the g-xTB 1.1.0 release (gxtb_parameters,
  basisq, eeq). crates/gxtb/src/data.rs and data_runtime.rs hold tables read from the g-xTB
  1.1.0 program; crates/gxtb/src/data_v2.rs holds the g-xTB 2.0.1 parameters read from the
  2.0.1 release binary (docs/gxtb-v2.0.1-spec.md says how). These make axtb-gxtb, and the
  builds that include it, GPL-3.0-only (LICENSE).
  T. Froitzheim, M. Mueller, A. Hansen, S. Grimme, ChemRxiv 2025,
  doi:10.26434/chemrxiv-2025-bjxvt.

gemm (https://github.com/sarah-quinones/gemm, https://github.com/sarah-quinones/gemm-x64-v2), MIT
  third_party/gemm-common (0.18.2) and third_party/private-gemm-x86 (0.1.22) are copies of
  these crates, dependencies of faer, with a patch to their cache-size detection
  (third_party/README.md). They keep their own LICENSE files. The patch applies to builds of
  this repository (the axtb program and the Python wheels), not to crates that depend on axtb
  from crates.io.
