Licensing & acknowledgements

Licensing & acknowledgements#

qc-rs is free software, and it stands on the shoulders of established scientific libraries. This appendix summarizes the license and credits the projects qc-rs builds on. The authoritative developer policy is docs/licensing.md.

The license#

qc-rs is licensed under the GNU Lesser General Public License v3.0 or later (LGPL-3.0-or-later; full text in COPYING.LESSER + COPYING). In plain terms: you can use it freely — including in commercial and closed-source work that links it — and modifications to qc-rs itself remain open. LGPL matches the quantum-chemistry ecosystem (Psi4, Dalton, PCMSolver, the Grimme tools, libxc) and, importantly, lets qc-rs faithfully port other LGPL/GPL-compatible reference implementations into Rust while staying open and linkable.

What qc-rs builds on#

Two external C/Fortran libraries are the hand-written foundations qc-rs links (not AI-authored — the exceptions to its vibe-coded development):

  • libcint (Dr. Qiming Sun) — the Gaussian-integral engine at the computational heart of every SCF.

  • libxc (Miguel A. L. Marques, Susi Lehtola, and collaborators) — the exchange–correlation functional library behind the DFT (xc=) methods.

And several reference implementations are faithfully ported into Rust (with attribution, reproducing their numbers):

qc-rs component

ported from

upstream license

pcm-core (PCM solvation)

PCMSolver

LGPL-3.0-or-later

qc-disp (DFT-D3/D4)

Grimme group s-dftd3 / dftd4 / mctc-lib

LGPL-3.0-or-later

GPU kernels (optional cuda)

gpu4pyscf gint/gvhf-rys/gdft

Apache-2.0 (vendored)

Geometry optimization uses geomeTRIC (Lee-Ping Wang).

Clean-room re-implementation (the Multiwfn case)#

The molecular-properties suite reproduces Multiwfn-class analyses, but Multiwfn’s license is incompatible with LGPL (it adds restrictions LGPL forbids). So qc-rs does not port Multiwfn’s source. Instead each analysis is re-implemented clean-room from the published method papers — algorithms and equations are not copyrightable, only code is — using Multiwfn (or PySCF) only as a black-box to validate the numbers, and citing the method papers. This is why the manual verifies every property number against an independent reference.

Note

Why this matters to you as a user Nothing here restricts using qc-rs — it is LGPL, so run it for anything, including commercial work. The policy above governs how the code is written and what it may incorporate. It also explains a design value you see throughout the manual: numbers are validated against trusted references, never guessed.

Acknowledgements#

qc-rs gratefully acknowledges libcint (Qiming Sun), libxc (Marques, Lehtola et al.), PCMSolver, the Grimme group (DFT-D3/D4), gpu4pyscf, geomeTRIC (Lee-Ping Wang), and PySCF (used as a validation reference). Full attributions live in each crate/file header and the repository README.md Acknowledgements.