No abstract

A survey of the geometry and environment of water molecules in crystalline hydrates is presented. Histograms and correlation analyses are based on 97 crystal structures accurately determined by neutron diffraction, and include data from 183 water molecules, each donating two hydrogen bonds. The sample is analyzed according to the nature of the hydrogen-bond acceptors and of the coordinated cations. Cases of bifurcated hydrogen bonds are also discussed. The hydrogen bonds tend to be linear and the acceptors tend to be located close to the water plane. The tendency of coordination bonds to be collinear with the direction of one of the lone pairs of the O or their bisector increases with the strength of the bonds.

No abstract

No abstract

Li−LSX (Li−faujasite with Si/Al = 1), cubic at room temperature, is orthorhombic (Fddd) at 10 K. In the room-temperature Fd3̄ phase, Li cations in the supercage are evenly distributed between 2-fold-coordinated sites III and III‘, in close agreement with the cation distribution in Na−X. The cubic−orthorhombic phase transition implies extensive redistribution of strain through the lattice and displacement of Li cations. In the low-temperature Fddd phase the occupancy of sites II is reduced, and nearly half the Li cations are in the supercage, most of them in a new site III‘, midway between neighboring sites II.