المؤلفون: Rinesh, T., Srinivasan, H., Sharma, V. K., Mitra, S.

المصدر: Journal of Chemical Physics; 7/14/2024, Vol. 161 Issue 2, p1-14, 14p

مصطلحات موضوعية: RELAXATION phenomena, LITHIUM perchlorate, HYDROGEN bonding, SOLVENTS, DIFFUSION kinetics, DIFFUSION

مستخلص: Aqueous mixtures of deep eutectic solvents (DESs) have emerged as a subject of interest in recent years for their tailored physicochemical properties. However, a comprehensive understanding of water's multifaceted influence on the microscopic dynamics, including its impact on improved transport properties of the DES, remains elusive. Additionally, the diffusion mechanisms within DESs manifest heterogeneous behavior, intricately tied to the formation and dissociation kinetics of complexes and hydrogen bonds. Therefore, it is imperative to explore the intricate interplay between bond kinetics, diffusion mechanism, and dynamical heterogeneity. This work employs water as an agent to explore their relationships by studying various relaxation phenomena in a DES based on acetamide and lithium perchlorate over a wide range of water concentrations. Notably, acetamide exhibits Fickian yet non-Gaussian diffusion across all water concentrations with Fickian ( τ f ) and Gaussian ( τ g ) timescales following a power-law relationship, τ g ∝ τ f γ , γ ∼ 1.4. The strength of coupling between bond kinetics and different diffusion timescales is estimated through various power-law relationships. Notably, acetamide–water hydrogen bond lifetime is linked to diffusive timescales through a single power-law over the entire water concentration studied. However, the relationship between diffusive timescales and the lifetime of acetamide–lithium complexes shows a sharp transition in behavior at 20 wt. % water, reflecting a change from vehicular diffusion below this concentration to structural diffusion above it. Our findings emphasize the critical importance of understanding bond dynamics within DESs, as they closely correlate with and regulate the molecular diffusion processes within these systems. [ABSTRACT FROM AUTHOR]

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المؤلفون: Srinivasan, H.^1,2 (AUTHOR), Sharma, V. K.^1,2 (AUTHOR), Mitra, S.^1,2 (AUTHOR) smitra@barc.gov.in

المصدر: Journal of Chemical Physics. 7/14/2021, Vol. 155 Issue 2, p1-12. 12p.

مصطلحات موضوعية: *LITHIUM perchlorate, *EUTECTICS, *PERCHLORATE removal (Water purification), *ACETAMIDE, *MOLECULAR dynamics, *TRANSLATIONAL motion, *ROTATIONAL motion

مستخلص: Deep eutectic solvents (DESs) have become a prevalent and promising medium in various industrial applications. The addition of water to DESs has attracted a lot of attention as a scheme to modulate their functionalities and improve their physicochemical properties. In this work, we study the effects of water on an acetamide based DES by probing its microscopic structure and dynamics using classical molecular dynamics simulation. It is observed that, at low water content, acetamide still remains the dominant solvate in the first solvation shell of lithium ions, however, beyond 10 wt. %, it is replaced by water. The increase in the water content in the solvent accelerates the H-bond dynamics by drastically decreasing the lifetimes of acetamide–lithium H-bond complexes. Additionally, water–lithium H-bond complexes are also found to form, with systematically longer lifetimes in comparison to acetamide–lithium complexes. Consequently, the diffusivity and ionic conductivity of all the species in the DES are found to increase substantially. Non-Gaussianity parameters for translational motions of acetamide and water in the DES show a conspicuous decrease with addition of water in the system. The signature of jump-like reorientation of acetamide is observed in the DES by quantifying the deviation from rotational Brownian motion. However, a notable decrease in the deviation is observed with an increase in the water content in the DES. This study demonstrates the intricate connection between H-bond dynamics and various microscopic dynamical parameters in the DES, by investigating the modulation of the former with addition of water. [ABSTRACT FROM AUTHOR]

المؤلفون: Srinivasan, H.^1,2 (AUTHOR), Sharma, V. K.^1,2 (AUTHOR), Mukhopadhyay, R.^1,2 (AUTHOR), Mitra, S.^1,2 (AUTHOR) smitra@barc.gov.in

المصدر: Journal of Chemical Physics. 9/14/2020, Vol. 153 Issue 10, p1-10. 10p.

مصطلحات موضوعية: *LITHIUM ions, *SOLVATION, *HYDROGEN bonding, *EUTECTICS, *INELASTIC neutron scattering, *ION transport (Biology), *DIFFUSION, *NEUTRON scattering

مستخلص: Lithium based deep eutectic solvents (DESs) are excellent candidates as eco-friendly electrolytes for lithium ion batteries. While some of these DESs have shown promising results, a clear mechanism of lithium ion transport in DESs is not yet established. This work reports the study on the solvation and transport of lithium in a DES made from lithium perchlorate and acetamide using Molecular Dynamics (MD) simulation and inelastic neutron scattering. Based on hydrogen bonding (H-bonding) of acetamide with neighboring molecules/ions, two states are largely prevalent: (1) acetamide molecules that are H-bonded to lithium ions (∼36%) and (2) acetamide molecules that are entirely free (∼58%). Analyzing their stochastic dynamics independently, it is observed that the long-range diffusion of the former is significantly slower than that of the latter. This is also validated from the neutron scattering experiment on the same DES system. Furthermore, the analysis of the lithium dynamics shows that the diffusion of acetamide molecules in the first category is strongly coupled to that of lithium ions. On an average, the lithium ions are H-bonded to ∼3.2 acetamide molecules in their first solvation. These observations are further bolstered through the analysis of the H-bond correlation function between acetamide and lithium ions, which shows that ∼90% of lithium ionic transport is achieved by vehicular motion where the ions diffuse along with their first solvation shell. It is also observed that the ionic motions are largely uncorrelated and the conductivity of lithium ions in the DES is found to be 11 mS/cm. The findings of this work are an important advancement in understanding solvation and transport of lithium in the DES. [ABSTRACT FROM AUTHOR]

المؤلفون: Sharma, V. K., Baiker, A.

المصدر: Journal of Chemical Physics; Dec1981, Vol. 75 Issue 12, p5596-5601, 6p

المؤلفون: Sharma, V. K.

المصدر: Journal of Chemical Physics; Jan1971, Vol. 54 Issue 2, p496-504, 9p