Effect of host framework on the diffusion process in microporous material: a molecular dynamics simulation...

Area of Science:

• Materials Science
• Physical Chemistry
• Computational Chemistry

Background:

• Microporous materials are crucial in various applications, with particle diffusion being a key process.
• A common assumption is that diffusing particles do not interact with framework atoms (Si, Al) due to steric hindrance from oxygen.
• This assumption simplifies diffusion models but may not accurately reflect reality.

Purpose of the Study:

• To investigate the validity of neglecting short-range interactions between diffusing particles and Si/Al atoms in microporous materials.
• To analyze the impact of these interactions on diffusion pathways and bottlenecks.
• To determine the effect on the self-diffusion coefficient (D) under different diffusion regimes.

Main Methods:

• Computational modeling to explore diffusion paths within the microporous framework.
• Calculation of guest-host interaction energies, including Si/Al interactions.
• Analysis of the self-diffusion coefficient (D) and activation energy in both linear and anomalous diffusion regimes.

Main Results:

• Short-range interactions between diffusing species and Si/Al atoms significantly affect the diffusion process.
• Guest-host interaction energy increases substantially when Si/Al interactions are considered.
• The self-diffusion coefficient (D) decreases in the linear regime but surprisingly increases in the anomalous regime due to decreased activation energy.

Conclusions:

• The assumption of neglecting Si/Al interactions in diffusion studies of microporous materials is not universally valid.
• These short-range forces play a critical role, influencing diffusion behavior differently across various regimes.
• Accurate modeling of diffusion requires incorporating these guest-host interactions for a comprehensive understanding.