A l arge variety of ions and molecules can b e i n s e

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Unformatted text preview: ntercalate is therefore constrained to a nearly t wod imensional region and thus provides a quasi-two-dimensional system whose physical properties can be studied. In particular the intercalated atoms have been observed to I u ndergo order-disorder transitions in a number of different systems ( 3 , 5 , 1 4, 1 8 , 1 9, 2 0, 2 1 , 2 3 , 3 6 ) . T h e order-disorder transitions in graphite intercalated compounds have attracted a great deal of attention. Parry and co-workers (10) w ere among the first to explore the ordering of intercalate species in graphite. have continued these investigations. Many others Clarke et. al. ( 24) u sed X-ray diffraction to investigate the order-disorder transition of cesium intercalated graphite, finding a discontinuity in the integrated intensity of various X-ray peaks around the order-disorder temperature T C , a nd Zabel et. al. ( 1 1 ) u sed the same technique to investigate the ordering of potassium in graphite. Leung and co-workers ( 12) w ere the first to report the infrared optic modes for stage 1 a nd stage 2 g raphite intercalated with potassium, rubidium and P age - 3c esium. Neutron diffraction studies were carried out on the same compounds by Zabel e t . a l . (13) who measured the [ 001] l ongitudinal acoustical and optical phonon branches and subsequently determined the force constants. They (13) found that the range and strength of the interplanar interaction increases upon intercalation with alkali atoms. Intercalate ordering has been observed in the intercalated layered dichalcogenide compounds. Features of the potential versus intercalate concentration curves ( 3) o f Li T iS x 2 w ere interpreted by Thompson ( 3 , 4 ) as evidence that t he lithium ions ordered between the T iS 2 l ayers. Berlinsky et. a l . (46) modeled the L ixTiSZ s ystem with a lattice gas model and their results appeared to support the suggestion that the lithium atoms ordered for certain intercalate concentrations ( x ) . T his ordering has never been observed experimentally in the L i T iS x 2 s ystem despite the fact that a n exhaustive search has been carried o u t . Investigations have been made at temperature...
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This note was uploaded on 10/08/2009 for the course CME MAT E 630 taught by Professor Dr. during the Fall '09 term at University of Alberta.

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