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Abstract: La0.8Ba1.2GaO3.9 · nH2O presents an interesting system with tetrahedral network of GaO4, and high oxide ion and proton conductivities. High-resolution quasielastic incoherent neutron scattering experiments were performed to gain better understanding of the proton conduction mechanism in tetrahedral systems. Translational long-range proton diffusion was observed. The activation energy for this process is 0.5eV. Mean-square-displacement of 0.7Å2 for protons was obtained for the temperature range where the long-range proton diffusion occurs. [Copyright &y& Elsevier]

A new ternary aluminide, LaNi(1 + x)Al(6 - x ) (x = 0.44), has been synthesized from La, Ni, and Al in sealed silica tubes. Its structure, determined by single-crystal X-ray diffraction, is tetragonal P4/mmm (No. 123) with Z = 1 and has the lattice parameters a = 4.200(8) and c = 8.080(8) angstroms. Refinement based on Fo2 yielded R1 = 0.0197 and wR2 = 0.020 [I > 2sigmaI]. The compound adopts a structure type previously observed in SrAu2Ga5 and EuAu2Ga5. The atomic arrangement is closely related to the one in BaAl4 as well as in other rare-earth gallide compounds such as LaNi0.6Ga6, HoCoGa5, Ce4Ni2Ga20, Ce4Ni2Ga17, Ce4NiGa18, and Ce3Ni2Ga15. This structure exhibits a large open cavity which may be filled by a guest atom. Band structure calculations using density functional theory have been carried out to understand the stability of this new compound., (Copyright 2004 American Chemical Society)