> ## Documentation Index
> Fetch the complete documentation index at: https://docs.ionworks.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Geometry & Capacity

> Compute electrode capacity, cell mass, cyclable lithium, and stoichiometry windows with ionworks-schema calculations.

Geometry and capacity calculations derive cell-level quantities from electrode dimensions and material properties. For the underlying equations and parameter definitions, see the [Geometry & Capacity Guide](/guide/calculations/geometry-capacity).

## Available calculations

| Schema                                                                     | Purpose                                                                                                       |
| -------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------- |
| `iws.calculations.ElectrodeCapacity(electrode=..., use_stoich_window=...)` | Solves the capacity equation for whichever quantity (`c_max`, `eps`, `L`, `A`, capacity, …) you didn't supply |
| `iws.calculations.CellMass()`                                              | Sums electrode, separator, and current-collector masses from densities and thicknesses                        |
| `iws.calculations.CyclableLithium()`                                       | Total shuttling lithium from electrode capacities and initial stoichiometries                                 |
| `iws.calculations.ElectrodeSOH()`                                          | Stoichiometry windows at 0% and 100% SOC from cell capacity and the electrode OCPs                            |
| `iws.calculations.StoichiometryLimitsFromCapacity(electrode=...)`          | Minimum/maximum stoichiometries from electrode capacity and excess-capacity values                            |

## Capacity from electrode geometry

```python theme={null}
import ionworks_schema as iws
from ionworks import Ionworks

known = iws.direct_entries.DirectEntry(
    parameters={
        "Positive electrode active material volume fraction": 0.65,
        "Positive electrode thickness [m]": 80e-6,
        "Electrode area [m2]": 0.1,
        "Maximum concentration in positive electrode [mol.m-3]": 51217.0,
        # … stoichiometry limits if use_stoich_window=True
    },
)

q_pos = iws.calculations.ElectrodeCapacity(electrode="positive")

pipeline = iws.Pipeline({"known": known, "Q_pos": q_pos})

client = Ionworks()
submission = client.pipeline.create(pipeline)
client.pipeline.wait_for_completion(submission.id)
result = client.pipeline.result(submission.id)
```

Supply any five of the six parameters in the capacity equation and `ElectrodeCapacity` returns the missing one. Set `use_stoich_window=True` when the capacity corresponds to a voltage window rather than the full material limit.

## Mass and energy density

```python theme={null}
import ionworks_schema as iws

mass = iws.calculations.CellMass()

pipeline = iws.Pipeline({
    "known": known,
    "cell_mass": mass,
})
```

The result adds `"Cell mass [kg]"` to the parameter set so downstream calculations (specific heat capacity, gravimetric energy density) can use it.

## Stoichiometry windows and cyclable lithium

```python theme={null}
import ionworks_schema as iws

pipeline = iws.Pipeline({
    "known": known,
    "Q_pos": iws.calculations.ElectrodeCapacity(electrode="positive"),
    "Q_neg": iws.calculations.ElectrodeCapacity(electrode="negative"),
    "esoh": iws.calculations.ElectrodeSOH(),
    "q_li": iws.calculations.CyclableLithium(),
})
```

`ElectrodeSOH` reads the cell capacity and electrode OCPs and produces the stoichiometries at 0% and 100% SOC for both electrodes. `CyclableLithium` then combines those with the electrode capacities to give the total lithium that shuttles during cycling.

<CardGroup cols={2}>
  <Card title="Geometry & Capacity (theory)" icon="shapes" href="/guide/calculations/geometry-capacity">
    The capacity equation, mass balance, and N/P-ratio theory.
  </Card>

  <Card title="Pipelines overview" icon="diagram-project" href="/pipelines/overview">
    How calculations chain with direct entries and data fits.
  </Card>
</CardGroup>