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Fluctuations in the μpT ensemble
Claudio A Cerdeiriña1, Jacobo Troncoso1
1Instituto de Física e Ciencias Aeroespaciais da Universidade de Vigo and Unidad MSMN Asociada al CSIC por el Instituto Blas Cabrera, Ourense 32004, Spain.
The Journal of Chemical Physics
|August 1, 2025
Summary
This study introduces a new statistical ensemble for open thermodynamic systems, linking fluctuations in properties to measurable responses. This framework precisely quantifies thermodynamic behavior and validates with a water-like model.
Area of Science:
- Statistical Mechanics
- Thermodynamics
- Physical Chemistry
Background:
- Macroscopic systems exchange heat, work, and matter with surroundings.
- Thermodynamic response functions characterize system behavior.
- Understanding fluctuations is key to macroscopic properties.
Purpose of the Study:
- Develop a statistical ensemble for completely open macroscopic systems.
- Connect variances and covariances of extensive properties to thermodynamic response functions.
- Generalize existing ensemble theories.
Main Methods:
- Derivation of exact formulas for variances and covariances.
- Analysis of ratios between extensive properties.
- Application to a water-like Ising model for numerical validation.
Main Results:
- Response functions quantify variances and covariances of property ratios.
- Formulas generalize to known ensembles (grand canonical, isothermal-isobaric).
- Numerical validation using an Ising model confirms theoretical predictions.
Conclusions:
- The derived ensemble provides a unified framework for open systems.
- It offers a deeper understanding of thermodynamic system behavior.
- The approach is consistent with established thermodynamic theories.
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