Pore Size Distributions in Porous Glasses:  A Computer Simulation Study

We have prepared a series of molecular models of porous glass using a recently developed procedure (Gelb, L. D.; Gubbins, K. E. Langmuir 1998, 14, 2097) that mimics the experimental processes that produce Vycor and controlled-pore glasses. We calculate nitrogen adsorption isotherms in these precisely characterized model glasses using Monte Carlo simulations. These isotherms are analyzed using the Barrett−Joyner−Halenda (BJH) method to yield pore size distributions, which are tested against exact pore size distributions directly measured from the pore structures. The BJH method yields overly sharp distributions that are systematically shifted (by about 1 nm) to lower pore sizes than those from our geometric method.