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SUMMARY:Understanding liquids and glass transition on the basis of elastic
  interactions - Kostya Trachenko
DTSTART:20090202T160000Z
DTEND:20090202T170000Z
UID:TALK15565@talks.cam.ac.uk
CONTACT:Ian Farnan
DESCRIPTION:Existing textbook expressions for the energy and heat capacity
  of gases and solids are widely taught in physics courses. However\, no su
 ch expression exists for a liquid. Based on the old idea of Frenkel\, I fo
 rmulate this problem in the language of phonons\, and calculate liquid ene
 rgy and heat capacity for both the classical and quantum cases.\n\nI subse
 quently address the old and very controversial problem of glass transition
 \, and propose the solution that is based on elastic interactions in a liq
 uid. Central to this discussion is the range of propagation of high-freque
 ncy elastic waves in a liquid\, which I call "liquid elasticity length d".
  d measures the range over which local relaxation events in a liquid elast
 ically interact with each other via the elastic waves they induce. d is sm
 all at high temperature\, and increases on lowering the temperature. This 
 sets the cooperativity of molecular relaxation in a liquid\, and gives the
  famous Vogel-Fulcher-Tammann law. In this picture\, I also discuss other 
 central properties of glass transition: the absence of divergence at a fin
 ite temperature\, the origins of two dynamic crossovers and the origin of 
 liquid "fragility" (Angell plot).\n\n
LOCATION:Harker 2 lecture room\, Department of Earth Sciences\, Downing Si
 te
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