ThermodynamicIntegration

The ThermodynamicIntegration step performs thermodynamic integration calculations, useful for free energy calculations and alchemical transformations.

The output file contains the value of:

\[\frac{\partial U}{\partial \lambda}\]

where U is the potential energy of the system and λ is the lambda value, the format is:

# 0.0
-500.5
-501.2
-499.8
...
# 0.1
-450.3
-451.1
-449.7
...

where the first line is the lambda value and the following lines are the value of the derivative of the potential energy with respect to lambda.

---

• type: ThermodynamicMeasure, ThermodynamicIntegration

• parameters:

  • outputFilePath: string: Path to the output file

  • stepLambda: int: Number of steps between lambda value changes

  • lambdaValues: real[]: List of lambda values to use

Example:

"thermodynamicIntegration":{
  "type":["ThermodynamicMeasure","ThermodynamicIntegration"],
  "parameters":{
    "intervalStep": 10000,
    "outputFilePath": "thermo_integration.dat",
    "intervalStep": 10000,
    "stepLambda": 10000,
    "lambdaValues": [0.0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0]
  }
}

Note

The output file will contain the lambda value and the corresponding dU/dλ for each step.

Warning

Ensure that your forcefield and integrator support lambda-dependent interactions when using this measure.

Tip

Thermodynamic integration is a powerful method for calculating free energy differences between two states of a system.