📚 Methods & API

Core calculations live in pythermocalcdb_nasa.app and return CustomProp objects from pythermodb_settings.

🧩 Common arguments

• component / reaction: Component or Reaction identifiers.
• temperature: Temperature(value, unit="K").
• model_source: built via pyThermoLinkDB.load_and_build_model_source(...) from component ThermoDB pickles.
• nasa_type: "nasa7" or "nasa9" (default "nasa9").
• basis: "molar" or "mass" for species properties.
• component_key: how components are keyed (e.g., "Name-Formula").
• mode (kwarg): "silent", "log", or "attach" for timing logs.

🔥 Species thermodynamic properties

Use these to evaluate NASA polynomials for a single component. Temperature breakpoints are selected automatically.

Function	Purpose	Args	Returns
H_T	Absolute enthalpy H°(T)	component, temperature, model_source, basis, nasa_type, component_key, **kwargs	CustomProp (value + unit + metadata) or None
S_T	Absolute entropy S°(T)	same as above	CustomProp or None
G_T	Gibbs free energy G°(T)	same as above	CustomProp or None
Cp_T	Heat capacity Cp(T)	same as above	CustomProp or None

from pythermocalcdb_nasa import H_T, S_T, G_T, Cp_T

H = H_T(component=CO2, temperature=T300K, model_source=model_source, basis="molar")
S = S_T(component=CO2, temperature=T300K, model_source=model_source, basis="mass")
G = G_T(component=CO2, temperature=T500K, model_source=model_source)
Cp = Cp_T(component=CH4, temperature=T600K, model_source=model_source)

See examples/exp-2.py for a full species workflow.

⚖️ Reaction thermodynamics and equilibrium

Helpers wrap species properties plus stoichiometry from pyreactlab_core.

Function	Purpose	Args	Returns
dH_rxn_STD	Reaction enthalpy change ΔH°(T)	reaction, temperature, model_source, nasa_type, component_key, **kwargs	CustomProp or None
dS_rxn_STD	Reaction entropy change ΔS°(T)	same as above	CustomProp or None
dG_rxn_STD	Reaction Gibbs free energy ΔG°(T)	same as above	CustomProp or None
Keq	Equilibrium constant from ΔG°(T)	reaction, temperature, model_source, nasa_type, component_key, **kwargs	CustomProp or None
Keq_vh_shortcut	van’t Hoff shortcut using ΔH°(298 K)	reaction, temperature, model_source, nasa_type, component_key, **kwargs	CustomProp or None

from pythermocalcdb_nasa import dH_rxn_STD, dS_rxn_STD, dG_rxn_STD, Keq, Keq_vh_shortcut
from pyreactlab_core.models.reaction import Reaction

reaction = Reaction(
    name="Water-Gas Shift",
    reaction="CO(g) + H2O(g) => CO2(g) + H2(g)",
    components=[CO, H2O, CO2, H2],
)

dH = dH_rxn_STD(reaction=reaction, temperature=T398K, model_source=model_source)
dS = dS_rxn_STD(reaction=reaction, temperature=T398K, model_source=model_source)
dG = dG_rxn_STD(reaction=reaction, temperature=T398K, model_source=model_source)

Keq_T = Keq(reaction=reaction, temperature=T1000K, model_source=model_source)
Keq_vh = Keq_vh_shortcut(reaction=reaction, temperature=T1000K, model_source=model_source, mode="log")

examples/exp-3.py shows the full reaction workflow.

🏗️ Building a model source

All calculations require a ModelSource. The examples build it from NASA pickles packaged in examples/thermodb:

from pythermodb_settings.models import Component, ComponentThermoDBSource
from pyThermoLinkDB import load_and_build_model_source

CO2 = Component(name="carbon dioxide", formula="CO2", state="g")
CO2_src = ComponentThermoDBSource(component=CO2, source="examples/thermodb/carbon dioxide-CO2-g-nasa-1.pkl")

model_source = load_and_build_model_source(
    thermodb_sources=[CO2_src],
    original_equation_label=False,  # normalize NASA labels
)

For generating new NASA pickles from a reference YAML, see examples/build-thermodb.py.