Composition dependent non-ideality in aqueous binary mixtures as a signature of avoided spinodal decomposition

Sarkar, Sarmistha; Banerjee, Saikat; Roy, Susmita; Ghosh, R. C.; Ray, Partha Pratim; Bagchi, Biman

doi:10.1007/s12039-014-0749-y

Cited by 12 publications

(8 citation statements)

References 53 publications

(32 reference statements)

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“…Požar et al studied the spatiotemporal heterogeneity of water/methanol mixtures at a wide range of temperatures. The amphiphilicity of methanol molecules reinforces the microheterogeneity of the structure even at room temperature as seen in aqueous solutions of other amphiphiles. ,− These microsegregated domains are longer lived at a lower temperature. The structural heterogeneity has a strong impact on the dynamic heterogeneity of the medium, which actually indicates the co-existence of mobile domains of different mobilities in the same system.…”

Section: Resultsmentioning

confidence: 99%

Breakdown of the Stokes–Einstein Relation in Supercooled Water/Methanol Binary Mixtures: Explanation Using the Translational Jump-Diffusion Approach

Dubey

Daschakraborty

2020

J. Phys. Chem. B

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A recent experiment has directly checked the validity of the Stokes−Einstein (SE) relation for pure water, pure methanol, and their binary mixtures of three different compositions at different temperatures. The effect of composition on the nature of breakdown of the SE relation is interesting. While in the majority of the systems, an increasing SE breakdown is observed with decreasing temperature, the breakdown is already significant at higher temperatures for the equimolar mixture. Violations of the SE relation in pure supercooled water at different temperatures and pressures have been previously explained using the translational jump-diffusion (TJD) approach, which provides a fundamental molecular basis, by directly connecting the SE breakdown with jump-diffusion of the molecules. We have used the same TJD approach for explaining the SE breakdown for the methanol/water binary mixtures of compositions studied in the experiment over a wide range of temperatures between 220 K and 300 K. We have understood that the jump-diffusion is the key responsible factor for the SE breakdown. The maximum jump-diffusion contribution gives rise to the early SE breakdown observed for the equimolar mixture observed in the experiment. This study, therefore, provides molecular insight into the SE breakdown for the supercooled water/methanol binary mixture, as found in the experiment.

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Section: Resultsmentioning

confidence: 99%

Breakdown of the Stokes–Einstein Relation in Supercooled Water/Methanol Binary Mixtures: Explanation Using the Translational Jump-Diffusion Approach

Dubey

Daschakraborty

2020

J. Phys. Chem. B

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“…Their work reveals that not all water and alcohol models show molecular aggregation. Banerjee and Bagchi 32,33 have shown that the existence of TBA clusters in the low TBA concentration is because of the so-called Janus effect. They have found that the lifetime of these clusters spans up to a few tens of picosecond for water-TBA mixture.…”

Section: Introductionmentioning

confidence: 99%

Three-dimensional Morphology and X-ray Scattering Structure of Aqueous tert-Butanol Mixtures: A Molecular Dynamics Study

Kaur

Kashyap

2017

J Chem Sci

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It is well established that water-alcohol mixtures exhibit anomalous properties at very low as well as at very high alcohol concentrations. Almost all the studies in this regard intend to link these anomalies to the microscopic structural changes as water (or alcohol) concentration increases in the mixture. However, it is important to note that the nature of these structural changes could be different at the water-and TBA-rich concentrations. In this article, our goal is to address such structural change overs, if really present, in the mixtures of water and tert-butanol (TBA) by using simulated X-ray scattering structure function, S(q), real space radial and spatial distribution functions and heterogeneity order parameter. By using a judicial partitioning scheme, we show that structural characteristic of pure water is qualitatively retained for X TBA < 0.1. The simulated S(q) peaks at around q=2 and q=2.8 Å −1 , which correspond to water oxygen correlations, begin to fade away only after X TBA ≥ 0.1. This is a clear indication of microscopic structural transition at X TBA ≈ 0.1. Beyond X TBA = 0.1, the TBA structural features begin to take over to that of water. The peak at q=1.3 Å −1 which primarily corresponds to nonpolar-nonpolar correlations in pure TBA begin to rise at X TBA ≈ 0.1. However, the pre-peak at around q=0.75 Å −1 , which is due to polar-polar and nonpolar-polar correlations in pure TBA, seems to appear at lower q value only at the equi-molar concentration of the mixture. From the solvent cage surrounding the TBA molecules, we observe that while the aggregation of TBA alkyl groups, due to hydrophobic interaction, is maximum at 10% TBA, the intervening hydrogen bonding interactions between water and TBA molecules tend to lower the hydrophobic interactions between the alkyl groups of alcohol with increasing concentration of TBA. In addition to this, we also observe dimers and small clusters of water molecules in the TBA-rich regime. The computed heterogeneity order parameters for the individual components of the mixture reveal enhanced non-uniform distribution of the TBA molecules near X TBA ≈ 0.1 to 0.3. These results are also supported by the radial distribution functions and nearest neighbour coordination numbers of water and TBA oxygen atoms around TBA oxygen.

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“…These quantities have a flat asymptote which corresponds to the value of the KBI according to Eqs. (4) and (9), which can be evaluated graphically. In the case of domain formation, the RKBI reach the asymptote through domain oscillations, which range can exceed the simulation box size.…”

Section: B Computational Detailsmentioning

confidence: 99%

“…7,8 However, the exact status of this microheterogeneity (MH), as well as the consequences of its existence upon thermophysical properties of such systems, is not well understood. 8,9 One point that we have investigated in our previous works 8 is how to distinguish the microheterogeneity (MH) from concentration fluctuations (CF), the latter which are accessible through the Kirkwood-Buff integrals [10][11][12] (KBI). The difference between CF and MH relates, respectively, to the k = 0 part of the structure factors (associated to the KBI) and the k 0 part corresponding to the pre-peak in partial structure factors associated with hydrogen bonding atoms.…”

Section: Introductionmentioning

confidence: 99%

The microscopic structure of cold aqueous methanol mixtures

Požar

Kerasidou

Lovrinčević

et al. 2016

The Journal of Chemical Physics

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The evolution of the micro-segregated structure of aqueous methanol mixtures, in the temperature range 300 K-120 K, is studied with computer simulations, from the static structural point of view. The structural heterogeneity of water is reinforced at lower temperatures, as witnessed by a pre-peak in the oxygen-oxygen structure factor. Water tends to form predominantly chain-like clusters at lower temperatures and smaller concentrations. Methanol domains have essentially the same chain-like cluster structure as the pure liquid at high concentrations and becomes monomeric at smaller ones. Concentration fluctuations decrease with temperature, leading to quasi-ideal Kirkwood-Buff integrals, despite the enhanced molecular interactions, which we interpret as the signature of non-interacting segregated water and methanol clusters. This study throws a new light on the nature of the micro-heterogeneous structure of this mixture: the domain segregation is essentially based on the appearance of linear water clusters, unlike other alcohol aqueous mixtures, such as with propanol or butanol, where the water domains are more bulky.

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Composition dependent non-ideality in aqueous binary mixtures as a signature of avoided spinodal decomposition

Cited by 12 publications

References 53 publications

Breakdown of the Stokes–Einstein Relation in Supercooled Water/Methanol Binary Mixtures: Explanation Using the Translational Jump-Diffusion Approach

Breakdown of the Stokes–Einstein Relation in Supercooled Water/Methanol Binary Mixtures: Explanation Using the Translational Jump-Diffusion Approach

Three-dimensional Morphology and X-ray Scattering Structure of Aqueous tert-Butanol Mixtures: A Molecular Dynamics Study

The microscopic structure of cold aqueous methanol mixtures

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