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SUMMARY:New understanding of collective modes and thermodynamics of the li
 quid state - Dr Kostya Trachenko (Queen Mary University of London)
DTSTART:20170914T100000Z
DTEND:20170914T110000Z
UID:TALK79241@talks.cam.ac.uk
CONTACT:Vanessa Blake
DESCRIPTION:A theory of liquids and liquid-glass transition requires under
 standing most basic thermodynamics properties of the liquid state such as 
 energy and heat capacity. This has turned out to be a long-standing proble
 m in physics. Landau&Lifshitz textbook states that no general formulas can
  be derived for liquid thermodynamic functions because the interactions ar
 e both strong and system-specific. Phrased differently\, liquids have no s
 mall parameter.\n\nRecent experimental and theoretical results open a new 
 way to understand liquid thermodynamics on the basis of collective modes (
 phonons) as is done in the solid state theory. There are important differe
 nces between phonons in solids and liquids\, and we have recently started 
 to\nunderstand and quantify this difference. I will review collective mode
 s in liquids including high-frequency solid-like transverse modes and will
  discuss how a gap in the reciprocal space emerges and develops in their\n
 spectrum [2]. This reduces the number of phonons with temperature\, consis
 tent with the experimental decrease of constant-volume specific heat with 
 temperature [1]. I will discuss the implication of the above theory for th
 e liquid-glass transition and the change of heat capacity at Tg.\n\nI will
  also mention how this picture can be extended above the critical point wh
 ere the recently proposed concept of the Frenkel line on the phase diagram
  separates liquid-like and gas-like states of supercritical dynamics [1].\
 n\n1. Trachenko\, K.\, and Brazhkin\, V. V.\, Collective modes and thermod
 ynamics of the liquid state\, Reports on Progress in Physics. 79\, 016502 
 (2016).\n\n2. C. Yang et al\, PRL 118\, 215502 (2017).
LOCATION:Lecture Theatre 3\, Department of Chemical Engineering and Biotec
 hnology\, West Cambridge Site
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