Self-diffusion Coefficient and Structure of Binary n-Alkane Mixtures at the Liquid-Vapor Interfaces

Area of Science:

• Physical Chemistry
• Materials Science
• Chemical Engineering

Background:

• Understanding liquid-vapor interfaces is crucial for chemical processes.
• n-alkane mixtures exhibit complex interfacial behavior.
• Molecular dynamics simulations provide insights into nanoscale phenomena.

Purpose of the Study:

• To investigate the molecular structure and self-diffusion coefficients in binary n-alkane liquid-vapor interfaces.
• To analyze the effect of molar fraction on interfacial composition and dynamics.
• To elucidate the relationship between molecular configuration and diffusion in confined liquid systems.

Main Methods:

• Molecular dynamics (MD) simulations were employed.
• Analysis of self-diffusion coefficients parallel to the interface.
• Examination of molecular alignment and local free volume.

Main Results:

• Hexane molecules accumulate in the liquid-vapor interface of hexane-tetracosane mixtures.
• Accumulation intensity decreases with increasing hexane molar fraction.
• Self-diffusion coefficients for both alkanes increase within the interface region.
• Diffusion is significantly higher on the vapor side at lower hexane concentrations.

Conclusions:

• Hexane enrichment and altered molecular configurations define the liquid-vapor interface.
• Increased local free volume drives enhanced diffusion in the interface.
• Simulation results offer fundamental understanding of interfacial transport phenomena in liquid mixtures.