Macroscopic relations for microscopic properties at the interface between solid substrates and dense fluids

Area of Science:

• Physics
• Physical Chemistry
• Materials Science

Background:

• Fluids confined by solid surfaces exhibit non-uniform properties due to atomic structuring.
• Local variations in state variables and transport coefficients at solid-fluid interfaces are influenced by wall characteristics.
• The exact mechanisms driving these interfacial phenomena remain unclear.

Purpose of the Study:

• To investigate local fluid properties at solid-fluid interfaces under varying surface conditions and temperatures.
• To derive microscopic relationships between fluid viscosity and density profiles in confined systems.
• To develop empirical models for predicting average fluid density and viscosity in channels.

Main Methods:

• Utilized nonequilibrium molecular dynamics (NEMD) simulations.
• Analyzed fluid behavior at the solid-fluid interface.
• Derived theoretical relationships and proposed empirical models.

Main Results:

• Demonstrated that local fluid properties are strongly dependent on surface conditions and temperature.
• Established microscopic connections between viscosity and density profiles for dense confined fluids.
• Developed practical, empirical relations for average density and viscosity based on temperature, wall interactions, and bulk properties.

Conclusions:

• Local fluid properties near solid surfaces are significantly influenced by confinement effects.
• The derived microscopic and empirical relations provide valuable insights into fluid behavior at interfaces.
• These findings are crucial for advancing micro-/nanofluidics, tribology, and understanding natural interfacial phenomena.