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SUMMARY:Understanding zeolites through the structural mechanics of infinit
 e frameworks - Dr Simon Guest\, CUED
DTSTART:20110225T140000Z
DTEND:20110225T150000Z
UID:TALK28574@talks.cam.ac.uk
CONTACT:Ms Helen Gardner
DESCRIPTION:Zeolites are microporous aluminosilicate minerals.  A zeolite 
 can be simply modelled as a set of vertex-pinned rigid tetrahedra: typical
 ly a silicon atom and four surrounding Oxygen atoms form a relatively stif
 f tetrahedron\, with each Oxygen atom common to two tetrahedra.  The Oxyge
 n acts as a spherical joint\, as the Si-O-Si bond angle is relatively flex
 ible.  The tetrahedra can be connected together in many different ways to 
 give zeolites with various voids and channels\, and this structure is esse
 ntial to their important uses as molecular sieves and catalysts.\n\n\nThe 
 interesting structural characteristic of zeolite frameworks is the equalit
 y between the number of rigid-body freedoms of the tetrahedra\, and the nu
 mber of constraints at the hinges.  In fact this implies that there must b
 e at least three inextensional deformation modes for the framework\, and t
 he presence of symmetry may increase this number.  This insight may have r
 elevance to understanding why there are a relatively small number of actua
 l zeolites (around 200)\, compared with the several million hypothetical s
 tructures that have been found.
LOCATION:Oatley Seminar Room\, Department of Engineering
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