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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.
- Fall '09