Partial molar enthalpies and reaction enthalpies from equilibrium molecular dynamics simulation

Area of Science:

• Computational Chemistry
• Chemical Engineering
• Thermodynamics

Background:

• Determining partial molar enthalpies in mixtures and chemical reactions traditionally requires complex simulation protocols.
• Existing methods often involve computationally expensive techniques like particle insertions, deletions, or identity changes.

Purpose of the Study:

• To introduce a new, efficient molecular simulation technique for calculating partial molar enthalpies.
• To demonstrate the method's applicability to both gas-liquid mixtures and systems with chemical reactions.
• To provide a direct route for determining reaction enthalpies from molecular dynamics (MD) simulations.

Main Methods:

• The new method utilizes small subsystems within a large reservoir and applies Hill's construction.
• It computes thermodynamic properties in the thermodynamic limit from small-scale fluctuations.
• The technique avoids particle insertions, deletions, or identity changes, simplifying the simulation process.

Main Results:

• The method accurately determines partial molar enthalpies in binary mixtures of Weeks-Chandler-Anderson particles.
• Results show excellent agreement when compared to conventional simulation techniques.
• Validation was also performed on a simple model mimicking a chemical reaction.

Conclusions:

• The developed molecular simulation technique is a valuable and efficient tool for calculating partial molar enthalpies.
• It offers a significant advantage for modeling chemical reactions by enabling direct determination of reaction enthalpies from a single MD simulation.
• This method enhances the capabilities of computational chemistry and chemical engineering research.