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The Quantum-Volume and Bragg-Williams Equations of State
1Department of Chemistry and Biomedical Science, NTNU - Norwegian University of Science and Technology, TrondheimNO-7481, Norway.
The Journal of Physical Chemistry. B
|July 27, 2026
Summary
This study introduces a lattice gas model combining quantum-volume and Bragg-Williams equations of state. The model accurately predicts thermodynamic properties and shows a heat capacity maximum near the critical temperature.
Area of Science:
- Thermodynamics
- Statistical Mechanics
- Physical Chemistry
Background:
- Existing equations of state often simplify intermolecular interactions.
- A need exists for models that incorporate both excluded volume and attractive forces.
Purpose of the Study:
- To develop and present an extended lattice gas model for thermodynamic property prediction.
- To incorporate intermolecular interactions and hard-core contributions into the quantum-volume equation of state.
- To provide analytical expressions for key thermodynamic properties.
Main Methods:
- Derivation of the quantum-volume (qv) equation of state from a lattice gas model.
- Extension of the qv equation with intermolecular interactions using the Bragg-Williams mean-field approach.
- Inclusion of a hard-core contribution to account for excluded volume effects.
Main Results:
- Analytical expressions for pressure, critical point, internal energy, isochoric heat capacity, and chemical potential were derived.
- The model demonstrates correct limiting behavior for ideal gases and dense systems.
- A notable maximum in isochoric heat capacity near the critical temperature was observed.
Conclusions:
- The extended lattice gas model provides a simplified yet effective framework for understanding thermodynamic behavior.
- The model's ability to predict key properties and phenomena like the heat capacity maximum makes it valuable for further research.
- This work lays the foundation for developing more complex and interpretable analytical models in molecular thermodynamics.
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