On Sun, 10 Oct 1999, Karl Cunningham wrote:
> Meredith --
> A couple of comments:
> At 09:39 PM 10/9/99 -0700, you wrote:
> >Bismuth
> >is one of those, -10.5 (s)on one, and -280.1 (I)
> >on another.  The (s) and (I) is not defined. A
> >number of items on the list also exhibit a
> >variation of values.  Tin is another one, with
> >+3.1 (White tin)to -37.0 for (gray tin).
> I don't know for sure, but I think the different susceptibilities for
> bismuth and tin are for different crystal structures.  Many materials'
> molecules can come together in more than one way, depending on the
> conditions present (temperature, pressure, rate of cooling, etc.) while the
> crystals are forming.

A good reference for mineral crystalline phases is Liu and Bassett, "Elements,
Oxides, Silicates: High Pressure Phases with Implications for the Earth's
Interior" Oxford Monographs on Geology and Geophysics No. 4. Oxford University
Press, 1986.  For the most part, different crystalline phases are more
difficult to make  by temperature alone.  Often pressure is also required to
make these things happen.  Bismuth has at least 6 known crystal structures at
room temperature, however ~2.5 GPa pressure is necessary to gain the first
transition.  We use this as a high pressure/low temperature calibrant at most
facilities in the world by observing resistivity changes while the press is
squeezing.  Bismuth may be melted at around 260-270 C but doesn't have any
other crystal phases from the first (standard conditions phase) to the melt.

John Hernlund
E-mail: hernlund@.......
WWW: http://www.public.asu.edu/~hernlund/

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