Structure of Dehydrated Zeolite Li−LSX by Neutron Diffraction:  Evidence for a Low-Temperature Orthorhombic Faujasite

Abstract

Li−LSX (Li−faujasite with Si/Al = 1), cubic at room temperature, is orthorhombic ( Fddd ) at 10 K. In the room-temperature Fd 3̄ 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.