A universal equation-of-state model based on single variable functions

Area of Science:

• Thermodynamics
• Physical Chemistry
• Materials Science

Background:

• Numerous existing equations of state (EOS) are complex or rely on empirical coefficients.
• These limitations hinder the application of current EOS theories across diverse material structures and intermolecular interactions.

Purpose of the Study:

• To develop a simple and universal equation of state (EOS) model.
• To establish a fully macroscopic thermodynamic approach for EOS development.
• To provide a new framework for understanding and applying thermodynamic principles.

Main Methods:

• Construction of two single-variable thermodynamic functions based on pressure and temperature.
• Thermodynamic derivation of two new EOS models in P-V-T and P-S-T forms.
• Utilizing a macroscopic thermodynamic approach without assumptions on material structure or intermolecular interactions.

Main Results:

• Developed two novel EOS models with forms comparable in simplicity to the ideal gas EOS.
• Ensured coefficients possess clear thermodynamic significance, enabling direct calculation without empirical fitting.
• Demonstrated the model's capability to accurately characterize substance thermodynamic properties.

Conclusions:

• The proposed universal EOS model offers a significant advancement over existing theories.
• The model is suitable for high-density and supercritical applications, expanding EOS utility.
• This work enriches fundamental thermodynamics and provides a new avenue for EOS theory development.