aerosolprops

Structure-derived pure-component properties for atmospheric organic aerosol.

aerosolprops is a modern successor to the pure-component property methods of UManSysProp (Topping et al., GMD 9, 899–911, 2016), rebuilt on RDKit as the structure engine and following the conventions of the thermo package family: strict SI units, estimators as pure functions of group counts where possible, and failures that return None rather than raise.

Status: pre-alpha. The repository currently contains the packaging skeleton, CI, documentation scaffold, the structure/topology foundation layers, and the first estimator (SIMPOL.1). The remaining methods below land one at a time, each with coefficients entered from the published papers and tests against literature values.

Methods (v0.1)

Boiling points used as inputs (by Myrdal–Yalkowsky and Nannoolal Part 3) can come from the self-implemented Nannoolal Part 1 route, from thermo's built-in Joback method, or from experimental data — aerosolprops does not reimplement Joback.

Installation

pip install aerosolprops

RDKit and thermo are required dependencies.

Design notes

• Units are strictly SI (Pa, K, mol); property failures return None.
• RDKit is the structure engine and a required dependency. It is imported lazily, and estimators ultimately consume group-count dictionaries — the same interface thermo uses for its own RDKit-optional group-contribution methods — so pieces remain extractable upstream.
• No molecular descriptors. Every method needs only 2D graph quantities: SMARTS substructure counts, ring perception, composition, and a few connectivity queries. No fingerprints, no 3D, no descriptor packages.
• No home-grown graph algorithms. The graph primitives (connected components, ring distances, neighbour queries) are RDKit built-ins; aerosolprops.topology only wraps them. What is method-specific is the translation of paper semantics (e.g. SIMPOL.1 "acid-side carbons", EVAPORATION "in-chain oxygen") onto those primitives.
• thermo compatibility. aerosolprops hard-depends on thermo and follows its group-contribution conventions ({group_id: coefficient record} catalogues, counts-based static estimators, Joback-style one-time fragmenting wrappers). Where a method's counting semantics do not fit thermo's mutually-exclusive SMARTS partition (SIMPOL.1's groups overlap and replace one another additively), aerosolprops ships its own fragmenter but keeps the same interface, so pieces can still be contributed upstream with minimal rework.

Licensing and data provenance

aerosolprops is MIT-licensed. Coefficients are entered from the published papers cited above (facts, not copyrightable expression), and SMARTS patterns are authored from the group definitions in those papers. UManSysProp is used only as a behavioural test oracle during development; no code or data files are copied from it.

Development

uv venv && uv pip install -e ".[test,docs]"
pytest                        # unit tests + doctests
mkdocs serve                  # documentation

CI runs the full test matrix (with doctests) on Linux/macOS/Windows for Python 3.9–3.14, plus a strict docs build.

License

MIT — see LICENSE.