Significant Liquid Structures, Vi. The Vacancy Theory of Liquids

Eyring, Henry; Ree, Taikyue

doi:10.1073/pnas.47.4.526

Cited by 139 publications

(46 citation statements)

References 7 publications

(8 reference statements)

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“…It is generally agreed that τ and viscosity in liquids are indeed governed by the temperature-activated process, with a caveat that U can include an additional temperature-dependent term due to cooperativity of molecular relaxation, in which case τ grows faster-than Arrhenius ("super-Arrhenius") as discussed below. This cooperative process is of the same nature as the one governing the non-exponentiality of relaxation in (16).…”

Section: Frenkel Reductionmentioning

confidence: 92%

Collective modes and thermodynamics of the liquid state

2015

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Strongly interacting, dynamically disordered and with no small parameter, liquids took a theoretical status between gases and solids, with the historical tradition of hydrodynamic description as the starting point. We review different approaches to liquids as well as recent experimental and theoretical work, and propose that liquids do not need classifying in terms of their proximity to gases and solids or any categorizing for that matter. Instead, they are a unique system in their own class with a notably mixed dynamical state in contrast to pure dynamical states of solids and gases. We start with explaining how the first-principles approach to liquids is an intractable, exponentially complex problem of coupled non-linear oscillators with bifurcations. This is followed by a reduction of the problem based on liquid relaxation time τ representing non-perturbative treatment of strong interactions. On the basis of τ , solid-like high-frequency modes are predicted and we review related recent experiments. We demonstrate how the propagation of these modes can be derived by generalizing either hydrodynamic or elasticity equations. We comment on the historical trend to approach liquids using hydrodynamics and compare it to an alternative solid-like approach. We subsequently discuss how collective modes evolve with temperature and how this evolution affects liquid energy and heat capacity as well as other properties such as fast sound. Here, our emphasis is on understanding experimental data in real, rather than model, liquids. Highlighting the dominant role of solid-like high-frequency modes for liquid energy and heat capacity, we review a wide range of liquids: subcritical low-viscous liquids, supercritical state with two different dynamical and thermodynamic regimes separated by the Frenkel line, highly-viscous liquids in the glass transformation range and liquid-glass transition. We subsequently discuss the fairly recent area of liquid-liquid phase transitions, the area where the solid-like properties of liquids have become further apparent. We then discuss gas-like and solid-like approaches to quantum liquids and theoretical issues that are similar to the classical case. Finally, we summarize the emergent view of liquids as a unique system in a mixed dynamical state, and list several areas where interesting insights may appear and continue the extraordinary liquid story.

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Section: Frenkel Reductionmentioning

confidence: 92%

Collective modes and thermodynamics of the liquid state

2015

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“…Until this MD paper, it had been generally held that diffusion in liquids took place through a series of rare, large distance jumps of molecules from "lattice sites" into vacancies or "holes" in a crystal-like lattice, the jump distance being roughly a molecular diameter. Historically, liquids were viewed as a crystal with many unoccupied sites [18], but Rahman's paper convincingly disproved this supposition. However, erratic, localised displacements have more recently been observed in the MD simulations of supercooled liquids near the glass transition, a phenomenon known as "heterogeneous dynamics" [19], so the defect-containing crystal view of a liquid is not entirely without merit.…”

Section: History Of Nemd Simulationsmentioning

confidence: 99%

Advances in nonequilibrium molecular dynamics simulations of lubricants and additives

2018

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Nonequilibrium molecular dynamics (NEMD) simulations have provided unique insights into the nanoscale behaviour of lubricants under shear. This review discusses the early history of NEMD and its progression from a tool to corroborate theories of the liquid state, to an instrument that can directly evaluate important fluid properties, towards a potential design tool in tribology. The key methodological advances which have allowed this evolution are also highlighted. This is followed by a summary of bulk and confined NEMD simulations of liquid lubricants and lubricant additives, as they have progressed from simple atomic fluids to ever more complex, realistic molecules. The future outlook of NEMD in tribology, including the inclusion of chemical reactivity for additives, and coupling to continuum methods for large systems, is also briefly discussed.

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“…(4), would directly result in a singularity (positive infinity). Thus, borrowing on an idea as first proposed by Eyring and Ree, 17 the 2PT method avoids this singularity by relating the DoS(v) of a liquid to two reference systems whose thermodynamics are easily calculated: …”

Section: Application To Single-particle Homogenous Liquidsmentioning

confidence: 99%

On the absolute thermodynamics of water from computer simulations: A comparison of first-principles molecular dynamics, reactive and empirical force fields

Pascal

Schärf

Jung

et al. 2012

The Journal of Chemical Physics

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We present the absolute enthalpy, entropy, heat capacity, and free energy of liquid water at ambient conditions calculated by the two-phase thermodynamic method applied to ab initio, reactive and classical molecular dynamics simulations. We find that the absolute entropy and heat capacity of liquid water from ab initio molecular dynamics (AIMD) is underestimated, but falls within the range of the flexible empirical as well as the reactive force fields. The origin of the low absolute entropy of liquid water from AIMD simulations is due to an underestimation of the translational entropy by 20% and the rotational entropy by 40% compared to the TIP3P classical water model, consistent with previous studies that reports low diffusivity and increased ordering of liquid water from AIMD simulations. Classical MD simulations with rigid water models tend to be in better agreement with experiment (in particular TIP3P yielding the best agreement), although the TIP4P-ice water model, the only empirical force field that reproduces the experimental melting temperature, has the lowest entropy, perhaps expectedly. This reiterates the limitations of existing empirical water models in simultaneously capturing the thermodynamics of solid and liquid phases. We find that the quantum corrections to heat capacity of water can be as large as 60%. Although certain water models are computed to yield good absolute free energies of water compared to experiments, they are often due to the fortuitous enthalpy-entropy cancellation, but not necessarily due to the correct descriptions of enthalpy and entropy separately.

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Significant Liquid Structures, Vi. The Vacancy Theory of Liquids

Cited by 139 publications

References 7 publications

Collective modes and thermodynamics of the liquid state

Collective modes and thermodynamics of the liquid state

Advances in nonequilibrium molecular dynamics simulations of lubricants and additives

On the absolute thermodynamics of water from computer simulations: A comparison of first-principles molecular dynamics, reactive and empirical force fields

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