Molecular mechanisms of hydrogen-loaded beta-hydroquinone clathrate

Molecular dynamics simulations are used to investigate the molecular interactions of hydrogen-loaded beta-hydroquinone clathrate. It is found that, at lower temperatures, higher loadings are more stable, whereas at higher temperatures, lower loadings are more stable. Attractive forces between the guest and host molecules lead to a stabilized minimum-energy configuration at low temperatures. At higher temperatures, greater displacements take the system away from the shallow energy minimum, and the trend reverses. The nature of the cavity structure is nearly spherical for a loading of one, leads to preferential occupation near the hydroxyl ring crowns of the cavity with a loading of two, and at higher loadings, leads to occupation of the interstitial sites (the hydroxyl rings) between cages by a single H(2) molecule with the remaining molecules occupying the equatorial plane of the cavity. Occupation of the interstitial positions of the cavities leads to facile diffusion.