Liquids

13 pages, 434 KiB

Open AccessArticle

Thermodynamic Scaling of the Shear Viscosity of Lennard-Jones Chains of Variable Rigidity

by Stephanie Delage Santacreu, Hai Hoang, Samy Khennache and Guillaume Galliero

Liquids 2021, 1(1), 96-108; https://doi.org/10.3390/liquids1010008 - 9 Dec 2021

Cited by 1 | Viewed by 2354

In this work, the thermodynamic scaling framework has been used to emphasize the limitations of fully flexible coarse grained molecular models to yield shear viscosity of real liquids. In particular, extensive molecular dynamics simulations have confirmed that, while being reasonable to describe the [...] Read more.

In this work, the thermodynamic scaling framework has been used to emphasize the limitations of fully flexible coarse grained molecular models to yield shear viscosity of real liquids. In particular, extensive molecular dynamics simulations have confirmed that, while being reasonable to describe the viscosity of short normal alkanes, the fully flexible Lennard-Jones and Mie chains force fields are inadequate to capture the density dependence of shear viscosity of medium to long alkanes. In addition, it is shown that such a weakness in terms of coarse grained molecular models can be readily quantified by using the thermodynamic scaling framework. As a simple alternative to these force fields, it is demonstrated that the insertion of a variable intramolecular rigidity in the Lennard-Jones chains model exhibits promising results to model medium to long chain-like real fluids from both thermodynamic and viscosity points of view. Full article

(This article belongs to the Section Physics of Liquids)

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19 pages, 1007 KiB

Open AccessArticle

Isochoric Specific Heat in the Dual Model of Liquids

by Fabio Peluso

Liquids 2021, 1(1), 77-95; https://doi.org/10.3390/liquids1010007 - 1 Dec 2021

Cited by 4 | Viewed by 2370

Abstract

We continue in this paper to illustrate the implications of the dual model of liquids (DML) by deriving the expression for the isochoric specific heat as a function of the collective degree of freedom available at a given temperature and analyzing its dependence [...] Read more.

We continue in this paper to illustrate the implications of the dual model of liquids (DML) by deriving the expression for the isochoric specific heat as a function of the collective degree of freedom available at a given temperature and analyzing its dependence on temperature. Two main tasks have been accomplished. First, we show that the expression obtained for the isochoric specific heat in the DML is in line with the experimental results. Second, the expression has been compared with the analogous one obtained in another theoretical dual model of the liquid state, the phonon theory of liquid thermodynamics. This comparison allows providing interesting insights about the number of collective degrees of freedom available in a liquid and the value of the isobaric thermal expansion coefficient, two quantities that are related to each other in this framework. Full article

(This article belongs to the Section Physics of Liquids)

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2 pages, 192 KiB

Open AccessEditorial

Welcome to Liquids: An Open Access Journal

by Enrico Bodo

Liquids 2021, 1(1), 75-76; https://doi.org/10.3390/liquids1010006 - 17 Nov 2021

Viewed by 1934

Abstract

We are thrilled to launch “Liquids” as a peer-reviewed open access journal [...] Full article

15 pages, 4626 KiB

Open AccessArticle

LiCoO₂/Graphite Cells with Localized High Concentration Carbonate Electrolytes for Higher Energy Density

by Xin Ma, Peng Zhang, Huajun Zhao, Qingrong Wang, Guangzhao Zhang, Shang-Sen Chi, Zhongbo Liu, Yunxian Qian, Jun Wang, Chaoyang Wang and Yonghong Deng

Liquids 2021, 1(1), 60-74; https://doi.org/10.3390/liquids1010005 - 10 Nov 2021

Cited by 6 | Viewed by 4564

Abstract

Widening the working voltage of lithium-ion batteries is considered as an effective strategy to improve their energy density. However, the decomposition of conventional aprotic electrolytes at high voltage greatly impedes the success until the presence of high concentration electrolytes (HCEs) and the resultant [...] Read more.

Widening the working voltage of lithium-ion batteries is considered as an effective strategy to improve their energy density. However, the decomposition of conventional aprotic electrolytes at high voltage greatly impedes the success until the presence of high concentration electrolytes (HCEs) and the resultant localized HCEs (LHCEs). The unique solvated structure of HCEs/LHCEs endows the involved solvent with enhanced endurance toward high voltage while the LHCEs can simultaneously possess the decent viscosity for sufficient wettability to porous electrodes and separator. Nowadays, most LHCEs use LiFSI/LiTFSI as the salts and β-hydrofluoroethers as the counter solvents due to their good compatibility, yet the LHCE formula of cheap LiPF₆ and high antioxidant α-hydrofluoroethers is seldom investigated. Here, we report a unique formula with 3 mol L⁻¹ LiPF₆ in mixed carbonate solvents and a counter solvent α-substituted fluorine compound (1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropylether). Compared to a conventional electrolyte, this formula enables dramatic improvement in the cycling performance of LiCoO₂//graphite cells from approximately 150 cycles to 1000 cycles within the range of 2.9 to 4.5 V at 0.5 C. This work provides a new choice and scope to design functional LHCEs for high voltage systems. Full article

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13 pages, 1743 KiB

Open AccessArticle

Density, Enthalpy of Vaporization and Local Structure of Neat N-Alkane Liquids

by Gerrick E. Lindberg, Joseph L. Baker, Jennifer Hanley, William M. Grundy and Caitlin King

Liquids 2021, 1(1), 47-59; https://doi.org/10.3390/liquids1010004 - 6 Aug 2021

Cited by 3 | Viewed by 3377

Abstract

The properties of alkanes are consequential for understanding many chemical processes in nature and industry. We use molecular dynamics simulations with the Amber force field GAFF2 to examine the structure of pure liquids at each respective normal boiling point, spanning the 15 n-alkanes [...] Read more.

The properties of alkanes are consequential for understanding many chemical processes in nature and industry. We use molecular dynamics simulations with the Amber force field GAFF2 to examine the structure of pure liquids at each respective normal boiling point, spanning the 15 n-alkanes from methane to pentadecane. The densities predicted from the simulations are found to agree well with reported experimental values, with an average deviation of 1.9%. The enthalpies of vaporization have an average absolute deviation from experiment of 10.4%. Radial distribution functions show that short alkanes have distinct local structures that are found to converge with each other with increasing chain length. This provides a unique perspective on trends in the n-alkane series and will be useful for interpreting similarities and differences in the n-alkane series as well as the breakdown of ideal solution behavior in mixtures of these molecules. Full article

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11 pages, 3399 KiB

Open AccessArticle

Investigation of Binary Liquids in Unstable States—An Experimental Approach

by Alexander Igolnikov, Sergey Rutin and Pavel Skripov

Liquids 2021, 1(1), 36-46; https://doi.org/10.3390/liquids1010003 - 28 May 2021

Cited by 5 | Viewed by 3024

Abstract

In this article, we present a methodology for conducting measurements based on pulse heating of a wire probe in partially soluble binary liquids. These liquids, which can be rapidly transferred to the region of unstable states above the diffusional spinodal, are novel research [...] Read more.

In this article, we present a methodology for conducting measurements based on pulse heating of a wire probe in partially soluble binary liquids. These liquids, which can be rapidly transferred to the region of unstable states above the diffusional spinodal, are novel research objects for the thermophysics of extreme states. Using the example of aqueous solutions of polypropylene glycol and glycol monobutyl ether having a lower critical solution temperature, the key hypothesis of the study on the general measurability of the properties of unstable solutions has been confirmed. The characteristic heating times from 1 to 15 milliseconds corresponded to the thickness of the heated layer comprising a few micrometers. The pressure was varied from units of MPa to 100 MPa. The conditions for the transition from measurements on pure components to those on solutions are formulated. The characteristic thermal patterns of the decay of unstable states depending on pressure and heating rate are revealed. The general possibility of using partially soluble binary liquids as a promising coolant in processes involving powerful local heat release is demonstrated. Full article

(This article belongs to the Section Physics of Liquids)

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11 pages, 1839 KiB

Open AccessArticle

Information Entropy of Regular Dendrimer Aggregates and Irregular Intermediate Structures

by Denis Sabirov, Alina Tukhbatullina and Igor Shepelevich

Liquids 2021, 1(1), 25-35; https://doi.org/10.3390/liquids1010002 - 5 Mar 2021

Cited by 7 | Viewed by 2987

Abstract

Dendrimer molecules and aggregates are chemical structures with regular branching that underlies their physicochemical properties. Regular dendrimers have been studied both theoretically and experimentally, but the irregular intermediate structures between the dendrimers of neighboring generations have not. In the present work, dendrimer aggregates, [...] Read more.

Dendrimer molecules and aggregates are chemical structures with regular branching that underlies their physicochemical properties. Regular dendrimers have been studied both theoretically and experimentally, but the irregular intermediate structures between the dendrimers of neighboring generations have not. In the present work, dendrimer aggregates, both regular and intermediate, are investigated in terms of the information entropy approach. As found, the information entropy of the regular dendrimer asymptotically increases with the generation number; herewith, its maximal value equals 2. The intermediate structures have been studied for the growing dendrimer G1 → G2 → G3 → G4 with the tricoordinated building block. The plot of the information entropy of the growing dendrimer on the size has the frontier consisting of the lowest values that correspond to the regular and irregular structures described with the symmetrical graphs. Other intermediate structures have information entropies higher than the regular dendrimers. Thus, to move the system from one informationally stable state to another, its information capacity must be temporarily increased. Full article

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24 pages, 2536 KiB

Open AccessArticle

Protolytic Equilibria in Organized Solutions: Ionization and Tautomerism of Fluorescein Dyes and Related Indicators in Cetyltrimethylammonium Chloride Micellar Solutions at High Ionic Strength of the Bulk Phase

by Nikolay O. Mchedlov-Petrossyan and Natalya A. Vodolazkaya

Liquids 2021, 1(1), 1-24; https://doi.org/10.3390/liquids1010001 - 20 Feb 2021

Cited by 9 | Viewed by 3570

Abstract

Ionic equilibrium of 22 hydroxyxanthenes, including halogen and nitro derivatives of fluorescein, and their thio- and aza analogues, were studied spectrophotometrically in micellar solutions of cetyltrimethylammonium chloride at ionic strength of the bulk phase 4.0 M KCl. This micellar pseudophase is characterized by [...] Read more.

Ionic equilibrium of 22 hydroxyxanthenes, including halogen and nitro derivatives of fluorescein, and their thio- and aza analogues, were studied spectrophotometrically in micellar solutions of cetyltrimethylammonium chloride at ionic strength of the bulk phase 4.0 M KCl. This micellar pseudophase is characterized by the electrostatic surface potential of +(15–16) mV and the

E_{T}^{N}

value of 0.623. In the case of dyes bearing the COOH group, colorless lactone is the predominant tautomer of the molecular form H₂R. A new classification of fluoresceins is developed. The dyes were divided into four groups based on the nature of tautomerism of the anions. In the case of the fluorescein type, the monoanions HR⁻ exist predominantly as “carboxylate” tautomers, with ionized carboxylic and non–ionized hydroxylic group. For the dyes of the eosin type, the situation is opposite, while for the intervening type of compounds, the concentrations of the two tautomers are comparable. Dyes capable of forming lactone anions HR⁻ were classified as the fourth type. For some of them, even the dianion R²⁻ exists as a lactone. The relationship between the stepwise ionization constants,

K_{a 1} / K_{a 2}

, varies from 1.3 to 1.07 × 10⁵ and is determined by the state of tautomeric equilibrium of molecules and ions. Full article

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Liquids, Volume 1, Issue 1 (December 2021) – 8 articles

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