prometheus.thermo_data.parsers.shomate

Loader/validator for the hand-authored NIST Shomate database (shomate.json).

Unlike the other parsers, Shomate data has no machine-readable raw source format — coefficients are looked up manually from the NIST WebBook (https://webbook.nist.gov) and the F coefficient is computed by hand to encode ΔfH°(298.15 K). This module therefore acts as:

1. A loader that reads and validates an existing shomate.json.

2. A template helper that prints a ready-to-paste JSON stub for a new species, to be filled in from NIST WebBook data.

Adding a new Shomate species

1. Look up A–E and G on the NIST Chemistry WebBook (Shomate equation tab).

2. Note ΔfH°(298.15 K) from JANAF or NIST-JANAF tables (kJ/mol).

3. Compute F so that H(298.15 K) = ΔfH°:

   t = 0.29815          # T / 1000 at 298.15 K
   polynomial_sum = A*t + B*t²/2 + C*t³/3 + D*t⁴/4 - E/t
   F = delta_f_H298_kJ_mol - polynomial_sum
   

4. Verify Cp and S at 298.15 K against literature.

5. Paste the output of ShomateParser.template() into shomate.json.

shomate.json schema

Keys starting with _ (e.g. _schema) are metadata and are skipped. Each species entry:

"<ID>": {
    "elements": {"Bi": 2, "O": 3},
    "phase":    "S",
    "alias":    "Bi2O3",          // optional
    "_note":    "...",             // optional verification note
    "segments": [
        {
            "t_low":        298.0,
            "t_high":       1097.0,
            "coefficients": [A, B, C, D, E, F, G, H]
        }
    ]
}

H (the 8th coefficient) is the NIST standard-enthalpy reference value and is stored for documentation purposes; it is not used in any calculation.

Classes

ShomateParser()

Load and validate a shomate.json file.

class prometheus_equilibrium.thermo_data.parsers.shomate.ShomateParser

Bases: object

Load and validate a shomate.json file.

This is a passthrough loader: the JSON is already in the compiled schema and requires no format translation. The parser validates required fields and normalises optional ones.

Usage:

db = ShomateParser().parse("shomate.json")
# db is a Dict[str, dict] ready for ThermoCompiler

parse(path: str) → Dict[str, dict]

Load path and return a validated dict keyed by species ID.

Entries whose keys start with _ are skipped (metadata). Species that fail validation are logged and excluded.

Returns:

{sp_id: record} in the shomate.json schema.

static template(elements: Dict[str, float], phase: str, t_low: float = 298.0, t_high: float = 1000.0, alias: str | None = None, delta_f_H298_kJ_mol: float | None = None) → str

Return a JSON stub for a new Shomate species, ready to paste into shomate.json.

Parameters:

• elements – Element dict, e.g. {"Bi": 2, "O": 3}.

• phase – Phase character: "G", "L", or "S".

• t_low – Lower temperature bound (K), default 298.0.

• t_high – Upper temperature bound (K), default 1000.0.

• alias – Human-readable name (optional).

• delta_f_H298_kJ_mol – ΔfH°(298.15 K) in kJ/mol (optional, for the note).

Returns:

Formatted JSON string suitable for copy-pasting into shomate.json.

Example:

print(ShomateParser.template({"Al": 2, "O": 3}, "S", alias="Al2O3"))