T his ordering has never been observed experimentally

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Unformatted text preview: s between 4 K a nd 3 0 0 K u sing X-ray diffraction techniques ( 23), n eutron scattering (48, 5 1 ) , l ight scattering ( 22), e lectron microscopy electrochemical methods ( 47, 49). ( 21), a nd It is now generally agreed that lithium does not order in T iS2 a bove 4 . 2 K . O n the other hand Dahn and M cKinnon ( 5 6 , 64) h ave recently obtained indirect evidence from electrochemical measurements for the ordering of lithium in T aS2. T hey have also suggested that second neighbour interactions may be responsible for Page - 4 s uppressing the order-disorder transition in the Li T i S x 2 s ystem. Intercalate ordering has been much easier to observe in other dichalcogenide intercalation systems. F or e xample, Boswell et. a 1 ( 18) u sed electron diffraction to observe the ordering of copper atoms in C uxNbS2 a nd Ridder et. a l . (20) used electron microscopy to investigate the ordering of copper atoms in Cu N bS a nd C uxTaS2. 2 x T he ordering of i ron atoms in Fe N bS w a s also studied by R oswell e t. al. x 2 (19) a s a function of temperature and composition using electron diffraction techniques. A gxTiS2 h as been one of the most thoroughly investigated of' the transition metal dichalcogenide intercalation compounds. The silver atom has a pseudo-alkali atomic structure having one electron in the outermost S-shell making it similar to the alkali metal atom lithium and yet is relatively inert compared to lithium. The A gxTiS2 s ystem is thus relatively easy to prepare and quite stable in a normal environment. Silver also has quite large X-ray and electron scattering cross-sections and experimental information is thus much easier to obtain from Ag T i S t han from a lithium x 2 intercalated compound. The pseudo-alkali properties of silver also suggest that many of the results obtained from A gxTiSZ s ystem will be applicable to t h e technologically more important Li T i S c ompound. x 2 P age - 5 T he first observation of an order-disorder transition in ~ Ag T iS w as made by Unger et. al. (21) who carried out x 2 I R aman s cattering and electron diffraction experiments on a n I e lectro-intercalated Ag...
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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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