Intercage guest correlations and guest clusters in high-pressure clathrate hydrates

The positions of guest atoms in high-pressure hexagonal Kr clathrate hydrate have been determined. Additionally, the large cage guests of the initial cubic form show a displacement of similar to 0.7 A degrees from the large cage center and exhibit reduced cage-to-cage correlations in guest positions; similar disorder likely carries over to the high-pressure form. Based on size and electron density maps, up to three atoms are located in the large cage of the high-pressure hexagonal form, where two Kr atoms are 2.25 A degrees above/below the cage center and one on a ring with a radius 1.70 A degrees from the cage center.