Skip to content

How to bypass automated NPT equilibration and enforce fixed-volume sampling for TI #238

@stargolike

Description

@stargolike

I am currently performing free energy calculations for liquid using thermodynamic integration (TI). For these metastable states, maintaining a strictly fixed density (fixed simulation cell volume) is critical to ensure the thermodynamic path connects the correct initial and target states.

For some metastable states, maintaining a strictly fixed density (fixed simulation cell volume) is critical to ensure the thermodynamic path connects the correct initial and target states.The ProblemBased on the runtime logs, calphy appears to execute an automated equilibration step at the beginning of the workflow:

calphy.helpers INFO At count 1 mean pressure is -9.610814 with 10.202168 vol/atom

This internal equilibration process (presumably employing an NPT ensemble or pressure relaxation) induces significant volume fluctuations. For supercooled liquids, any lattice or volume relaxation deviates the system from the pre-optimized input configuration, effectively rendering the calculated Gibbs free energy invalid for the specific density of interest.

To maintain the integrity of the metastable thermodynamic integration, I need calculate TI without any initial box relaxation.

Dear developers, could this equilibration process be banned? How can it be banned?

Metadata

Metadata

Assignees

No one assigned

    Labels

    No labels
    No labels

    Type

    No type
    No fields configured for issues without a type.

    Projects

    No projects

    Milestone

    No milestone

    Relationships

    None yet

    Development

    No branches or pull requests

    Issue actions