Open Conference Systems, StatPhys 27 Main Conference

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New understanding of collective modes and thermodynamics of liquid and supercritical states
Kostya Trachenko

##manager.scheduler.building##: Edificio San Jose
##manager.scheduler.room##: Aula 110/111
Date: 2019-07-08 04:15 PM – 04:30 PM
Last modified: 2019-06-08

Abstract


A theory of liquids and liquid-glass transition requires understanding
most basic thermodynamic  properties of the liquid state such as energy and heat capacity. This has turned out to be a long-standing problem in physics [1]. Landau&Lifshitz textbook states that no general formulas can be derived for liquid thermodynamic functions because the interactions are both strong and system-specific. Phrased differently, liquids have no small parameter.

Recent 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 differences between phonons in solids and liquids, and we have recently started  to  understand and quantify this difference. I will review collective modes in liquids including high-frequency solid-like transverse modes and will discuss how a gap in the reciprocal space emerges and develops in their spectrum [2]. This reduces the number of phonons with temperature,  consistent with the experimental decrease of constant-volume specific heat with temperature [1].  I will discuss the implication of the above theory for fundamental understanding of liquids. I will also mention how this picture can be extended above the critical point where the recently proposed Frenkel line on the phase diagram separates liquid-like and gas-like states of supercritical dynamics [1,3-5].

1. K. Trachenko and V. V. Brazhkin, Collective modes and thermodynamics of the liquid state, Reports on Progress in Physics 79, 016502 (2016).
2. C. Yang, M. T. Dove, V. V. Brazhkin and K. Trachenko, Physical Review Letters 118, 215502 (2017).
3. V. V. Brazhkin and K. Trachenko, Physics Today 65(11), 68 (2012).
4. V. V. Brazhkin et al, Physical Review Letters 111, 145901 (2013).
5. D. Bolmatov, V. V. Brazhkin and K. Trachenko, Nature Comm. 4:2331 (2013).