# Choose Phases

The "Phases" field is utilized to select the phases expected to form in the system. This field is an array of strings and must include the "aqueous (liquid1)" phase at a minimum. It is required for chemistry file generation, and the selected phases impact the chemistry model. 

Below is an example of the "Phases" field:

```json
{
    "params": {
    "thermodynamicFramework": "Aqueous (H+ ion)", 
    "modelName": "testModel",
      "phases": [
        "liquid1",
        "vapor",
        "solid", 
        "liquid2"
      ],
        "inflows": [
            {
                "name": "H2O"
            },
            {
                "name": "NACL"
            }
        ]
    }
}
```

| phase   | value   |
| ------- | ------- |
| aqueous | liquid1 |
| vapor   | vapor   |
| solid   | solid   |
| organic | liquid2 |

Here are the requirements and assumptions you need to be aware of:

1. For DBS file generation, the "phases" field must be explicitly entered by the user and cannot be left empty (e.g., `"phases":[]` is incorrect).
2. The aqueous phase or "liquid1" phase should always be specified (e.g., `"phases": ["vapor", "solid"]` is incorrect).
3. The order or sequence of phase names does not matter.
4. Duplicate phase names are not allowed (e.g., `"phases": ["liquid1", "liquid1", "vapor", "solid"]` is incorrect).
5. In the Aqueous and MSE-SRK models, the vapor phase is required to model the organic phase. Thus, the vapor phase will be automatically selected by default if the organic phase is enabled.
6. In query methods, if a user doesn't specify any phases explicitly, "liquid1" or aqueous phase, "vapor", and "solid" will be enabled by default. The "liquid2" or organic phase is not included.


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