Studies of diffusion coefficients in disordered porous matrices confined in a slit-pore

Abstract

We present a series of molecular dynamics simulations to study the structure of porous matrices confined in a slit-pore. The matrices were prepared by two different methods. In the first method we used direct simulations of a fluid at a fixed density and the matrix was taken from the last configuration of its particles. In the second method we simulated a binary mixture where one of the components served as a template material and the final porous matrix configuration was obtained by removing template particles from the mixture. In both methods the matrices were confined by two parallel walls (slit-pore) modeled by continuous solid surfaces. The results show that the matrix structure and porosity were affected by the method of preparation of the porous matrices. Moreover, we found smaller void cavities in these matrices than in matrices prepared without walls. Finally, diffusion of a fluid inside the matrices was investigated and it was found that the diffusion coefficient did not decrease with the fluid density, and presented a maximum at certain values of the fluid density.

Keywords:

• Porous matrices
• Confined systems
• Diffusion
• Computer simulations

Acknowledgements

JFS acknowledges a scholarship from IIM-UNAM and we also acknowledge support from CONACyT-México through grant 42842-F and DGAPA-UNAM México through grant IN102207-3. We also thank the reviewer for his valuable comments, which improved the manuscript.