Perspectives on Molecular-Level Understanding of Thermophysics of Liquids and Future Research Directions

Chen, Gang

doi:10.1115/1.4052657

Cited by 20 publications

(37 citation statements)

References 142 publications

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“…One line of thought tries to understand transport in liquids by modifying the Boltzmann theory of gas, as represented by the effort of Enskog (see ref. [9] in [7]). Another line was pioneered by Einstein ([see ref.…”

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confidence: 98%

“…Many studies and books have been devoted to understanding liquids, and significant progress has been made ( [5,8,9], see also Refs. [8,9,15,[23][24][25][26][27][28][29][31][32][33][34][35][36][37][38] of [7]). Despite that, our current ability to predict the thermodynamic and 3 transport properties of liquids is still lacking.…”

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confidence: 99%

“…Starting from the experimental results obtained in various liquids with IXS techniques, [see for example [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28], the evidence that ephemeral pseudo-crystalline structures "exist and persist" in liquids has gradually consolidated [7,[43][44], their size and number depending on the liquid temperature (and pressure). This picture resembles in some way that currently accepted for water, that is believed to consist of hydrogen-bonded clusters in dynamic equilibrium [7]. It is worth noticing, among others, the pioneering experimental investigations by Grimsditch [43] and those by Giordano and Monaco [44], who performed first measurements across the glass-liquid and solid-liquid transitions, respectively.…”

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Mesoscopic collective dynamics in liquids and the Dual Model

Peluso

2022

Preprint

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Here in this paper a microscopic vision is presented of a Dual Model of Liquids (DML) starting from a solidpicture. The task is accomplished firstly by showing how a series of experimental evidences and theoreticaldevelopments on liquid modelling, gathered for the first time, can be framed in a mesoscopic view of liquids,hypothesized as constituted by a population of dynamic aggregates of molecules, diving in an ocean of amorphousliquid. The pseudo-crystals interact with the rest of the liquid through harmonic elastic waves and anharmonic wavepacketspropagating within and among the structures, respectively. The interaction term is derived from “firstprinciples”; its anharmonic character allows the exchange of both energy and momentum between the wave packetsand the molecule’ clusters, determining the displacement of the latter within the medium, and the redistribution of theenergy between external degrees of freedom (DoF) and internal collective degrees of the clusters. Among the noveltiesof this model is that, making use of a simple kinetic mechanism, it provides quantitative expressions of variousextensive thermophysical quantities, introducing the statistical number of excited DoF. In this way the problem isbypassed of other dual models which are sometimes unable to correctly reproduce the expressions for thosethermophysical quantities showing deviations due to the activation/deactivation of internal DoF. The interpretation ofthe relaxation times is given, their Order-of-Magnitude calculated and the way in which these times are involved in thedifferent phases of the collective dynamics of liquids discussed.Because this model appears complementary to the Phonon theory of Liquid Thermodynamics (PLT), acomparison is provided with results obtained in the frame of PLT, as well with the forecasts for the visco-elastictransition regions and with systems exhibiting k-gap.In the last part of the paper, theoretical insights and experiments are suggested as potential directions for futureresearches and developments.

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confidence: 98%

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confidence: 99%

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confidence: 99%

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Mesoscopic collective dynamics in liquids and the Dual Model

Peluso

2022

Preprint

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“…These two facts represent two of the main obstacles that physicists have to face in modelling the liquid state of matter. Various lines of thought have been developed over the past 150 years, as Chen reports in a very recent paper [7] where he has reviewed in critical way the several existing molecular pictures and theoretical approaches on liquids, followed with elaborations on different models developed for several extensive liquid quantities, such as the specific heat, thermal conductivity, and viscosity. The review shows, as the author himself underlines, that "current understanding of thermophysical properties of liquids is still poor and theoretical tools to study them are not well developed yet".…”

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confidence: 99%

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confidence: 99%

Mesoscopic Collective Dynamics in Liquids and the Dual Model

Peluso¹

2022

Journal of Heat Transfer

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A microscopic vision is presented of a Dual Model of Liquids starting from a solid picture. The task is accomplished firstly by showing how a series of experimental evidences and theoretical developments, gathered for the first time, can be framed in a mesoscopic view of liquids, hypothesized as constituted by a population of dynamic aggregates of molecules diving in an ocean of amorphous liquid. The pseudo-crystals interact with the rest of the liquid through harmonic waves and anharmonic wavepackets propagating within and among the structures. The interaction term is derived from "first principles"; its anharmonic character allows the exchange of energy and momentum between the wave packets and the molecule' clusters, determining the displacement of the latter within the medium and the redistribution of the energy between external degrees of freedom (DoF) and internal collective degrees. Among the novelties is that it allows calculating various thermophysical quantities by introducing the statistical number of excited DoF. In this way, the problem is bypassed of other dual models which are sometimes unable to correctly reproduce those thermophysical quantities showing deviations due to the activation/deactivation of internal DoF. The interpretation of the relaxation times is given, their Order-of-Magnitude calculated and compared with experimental data. A comparison is provided with results obtained in the frame of the Phonon theory of Liquid Thermodynamics, as well with systems exhibiting k-gap.In the last part of the paper theoretical insights and experiments are suggested as potential directions for future research and developments.

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Cluster‐associate viscosity model of tin chloride in comparison with the Frenkel model

Bekbayeva,

Makasheva,

Malyshev

et al. 2023

Heat Trans

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Determining the viscosity of inorganic molten compounds like tin chloride is critically important for material processing, chemical synthesis, and energy applications. However, experimental limitations have restricted the development of accurate viscosity models. This study tests a new cluster‐associate model for predicting the viscosity of molten tin chloride across a wide temperature range. The model links viscosity to the structure and dynamics of molecular clusters in the melt. The aim of this study is to establish a correlation between viscosity and cluster formation within a liquid, using tin chloride as an example. The data were calculated using a newly developed equation based on the concept of randomized particles. The temperature range studied was from the melting point to the boiling point. To verify the accuracy of the cluster‐associate model, it was compared with the Frenkel equation using logarithmic coordinates. Simulations were performed on tin chloride, which yielded results showing a linear relationship between the degree of cluster association and the activation energy of fluidity. The proportionality coefficient reflects the activation energy associated with a single cluster. The Frenkel equation in the logarithmic coordinate scale was compared with the cluster‐associate model. The functional dependence and correspondence of these models are indicated by their high coefficient mutual correlation. The proposed viscosity model underwent testing for the entire liquid state range of the substance, and calculations confirmed its validity. This enables reliable use of the suggested model for both high‐ and low‐temperature extrapolation, including the critical point region.

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Perspectives on Molecular-Level Understanding of Thermophysics of Liquids and Future Research Directions

Cited by 20 publications

References 142 publications

Mesoscopic collective dynamics in liquids and the Dual Model

Mesoscopic collective dynamics in liquids and the Dual Model

Mesoscopic Collective Dynamics in Liquids and the Dual Model

Cluster‐associate viscosity model of tin chloride in comparison with the Frenkel model

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