Molecular Dynamics Simulation Study of Solid Vibration Permeation in Microporous Amorphous Silica Network Voids

Area of Science:

• Materials Science
• Chemical Engineering
• Computational Chemistry

Background:

• Microporous silica membranes exhibit pore sizes below 3 Å, enabling transport of small gas molecules like helium and hydrogen.
• These membranes are promising for hydrogen (H2) separation due to their selective pore structure.

Purpose of the Study:

• To investigate gas permeation mechanisms within the nanopores of silica membranes.
• To analyze the influence of membrane structure and atomic thermal motion on gas transport properties.

Main Methods:

• Utilized membrane permeation molecular dynamics (MD) simulations, including non-equilibrium MD (NEMD).
• Employed classic harmonic oscillation potential to model thermal motion of silica membrane atoms.
• Analyzed gas diffusivity and permeability using gas translation (GT) and solid vibration (SV) models.

Main Results:

• Simulations successfully replicated gas permeation characteristics in amorphous silica membranes.
• Oscillative thermal motion of membrane atoms was found to enhance gas diffusivity.
• The solid vibration (SV) model provided a more realistic geometrical representation and accurately explained both gas diffusivity and permeability for helium and hydrogen.

Conclusions:

• The solid vibration model effectively explains the temperature-dependent behavior of helium and hydrogen gas diffusion and permeability in silica membranes.
• The findings support the viability of microporous silica membranes for efficient hydrogen separation.