Determination of Pore Accessibility in Disordered Nanoporous Materials

Abstract

We propose a new algorithm based on application of cluster analysis to group adsorbate molecules of a highly dense adsorbed phase in the atomistic structural model of a disordered material into connected and disconnected clusters, through which pore network connectivity of the material is identified. Our proposed algorithm is then validated using a synthetic pore structure, as well as the reconstructed structure of a saccharose char obtained in our recent work using hybrid reverse Monte Carlo simulation.1 The algorithm also identifies kinetically closed pores in the latter structural model that are not accessed by adsorbate molecules at low temperature, at which their kinetic energy cannot overcome potential barriers at the mouths of pores that can otherwise accommodate them. The results are validated by transition state theory calculations for N2 and Ar adsorption, showing that N2 can equilibrate in narrow micropores at practical time scales at 300 K, but not at 77 K. Large differences between time scale...