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SUMMARY:Simplifying the theory of the Invar effect in iron-nickel alloys -
  Chris Hooley (SUPA\, University of St Andrews)
DTSTART:20090828T143000Z
DTEND:20090828T153000Z
UID:TALK19616@talks.cam.ac.uk
CONTACT:Dr Jonathan Keeling
DESCRIPTION:Zero-temperature ab initio calculations of the lattice spacing
  of \ndisordered iron-nickel alloys are presented.  These show a strong ne
 gative \ncorrelation between the lattice spacing and the number of \nneare
 st-neighbour iron-iron pairs with antiparallel local moments.  Based \non 
 the conjecture that this correlation persists at non-zero temperature\, \n
 a simple theory is formulated that reproduces several experimental results
  \non this class of Invar materials.  We conclude that an alloy shows the 
 \nInvar effect if the concentration of such pairs increases sufficiently \
 nrapidly over a broad interval of temperature.\n\nSome of this work is ava
 ilable as a preprint\, "arXiv:0811.3673":http://www.arxiv.org/abs/0811.367
 3.
LOCATION:TCM Seminar Room\, Cavendish Laboratory
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