Additionally, we computed the porosity of the glasses (see Figure ) and found a total porous volume of 4.6 cm 3 kg -1 for the ReaxFF glass, down from the 54 cm 3 kg -1 of the crystal (computed for ab initio). As the porosity is greatly impacted by the density of a system, direct comparison to the ab initio glass (68 cm 3 kg -1 ) is limited but does suggest that the ReaxFF glass porosity is one order of magnitude too low. This all but complete loss of porosity also contradicts the experimental measurements of the porosity of a ZIF-4 glass made by positron annihilation lifetime spectroscopy (PALS), and further confirms that the density of the ReaxFF glass is excessively large.