LambdaCycle

The LambdaCycle step implements a cyclic lambda schedule for alchemical transformations or free energy calculations. It allows for repeated cycles of lambda changes, useful for measuring free energy of particles immersed in a solvent. The cycle consists of a series of steps for each lambda value, followed by a pause step before the next cycle begins. The cycle is repeated until the simulation is complete.

lambda=1                        ...................                               ...................
lambdaValues[n]              ...                                               ...
    .......               ...                                               ...
    .......            ...                                               ...
lambdaValues[0]     ...                                               ...
lambda=0                                           ...................                               ...................
startStep ---------><-><-><-><-><---measureStep---><----pauseStep----><-><-><-><-><---measureStep---><----pauseStep---->
                     |
                     |
                     L-> activationStep

---

• type: FlowControl, LambdaCycle

• parameters:

  • activationStep: int: Number of steps for each lambda activation phase

  • measureStep: int: Number of steps for measurement at each lambda value

  • pauseStep: int: Number of steps for pause between cycles

  • lambdaValues: real[]: List of lambda values to cycle through

Example:

"lambdaCycle":{
  "type":["FlowControl","LambdaCycle"],
  "parameters":{
    "activationStep": 1000,
    "measureStep": 5000,
    "pauseStep": 2000,
    "lambdaValues": [0.0, 0.2, 0.4, 0.6, 0.8, 1.0]
  }
}

Note

This step is particularly useful for enhanced sampling techniques like lambda dynamics.

Warning

Careful consideration of the cycle parameters is necessary to ensure proper equilibration and sampling at each lambda value.