Communication: Probing the existence of partially arrested states in ionic liquids

Ramírez-González, Pedro E.; Sánchez-Díaz, Luis E.; Medina‐Noyola, Magdaleno; Wang, Yanting

doi:10.1063/1.4967518

Cited by 17 publications

(14 citation statements)

References 37 publications

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“…For the AA model, the MSD in the diffusive regime is higher for the cations than for the anions at low temperatures, whereas the discrepancy vanished at high temperatures. The observation that larger cations diffuse faster than smaller anions was recently attributed to the diffusion of cations through a glassy network of anions . For the CG model, the MSD in the diffusive regime is comparable for both ionic species, with a tendency for faster diffusion of cations at low temperatures and of anions at high temperatures.…”

Section: Resultsmentioning

confidence: 91%

Role of Dynamic Heterogeneities in Ionic Liquids: Insights from All‐Atom and Coarse‐Grained Molecular Dynamics Simulation Studies

Pal

Vogel

2017

ChemPhysChem

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We performed molecular dynamics simulations for the room-temperature ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate ([Bmim][PF ]). By employing all-atom (AA) and coarse-grained (CG) models, we compared the characteristic times of various dynamical modes, from vibration to diffusion, and the importance of dynamical heterogeneities at different levels of chemical resolution and over broad temperature ranges. It was shown that coarse graining leads to a substantial speedup in molecular dynamics, whereas it weakly affects the strength of dynamical heterogeneities. Despite the general speedup, several relationships between dynamical modes on different timescales were preserved. In particular, the heterogeneity timescales of the AA and CG models collapse onto the same curve as a function of the structural (α) relaxation time τ . Moreover, vibrational amplitudes and relaxation times τ are related at both levels of chemical resolution. We argue that the robustness of these relationships assists the development of dynamically consistent coarse-graining strategies and justifies the use of simplified models for a theoretical understanding of viscous liquids.

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Section: Resultsmentioning

confidence: 91%

Role of Dynamic Heterogeneities in Ionic Liquids: Insights from All‐Atom and Coarse‐Grained Molecular Dynamics Simulation Studies

Pal

Vogel

2017

ChemPhysChem

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“…Further studies on charge transport showed the difference of RTILs to conventional electrolyte solutions [109] . Slower diffusion of smaller anions compared with large cations, were reported over a wide range of temperatures, i. e. formation of a strongly repulsive glass by the anions – termed arrested states [110] …”

Section: Resultsmentioning

confidence: 99%

Understanding the Photoexcitation of Room Temperature Ionic Liquids

2020

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Photoexcitation of (neat) room temperature ionic liquids (RTILs) leads to the observation of transient species that are reminiscent of the composition of the RTILs themselves. In this minireview, we summarize state‐of‐the‐art in the understanding of the underlying elementary processes. By varying the anion or cation, one aim is to generally predict radiation‐induced chemistry and physics of RTILs. One major task is to address the fate of excess electrons (and holes) after photoexcitation, which implies an overview of various formation mechanisms considering structural and dynamical aspects. Therefore, transient studies on time scales from femtoseconds to microseconds can greatly help to elucidate the most relevant steps after photoexcitation. Sometimes, radiation may eventually result in destruction of the RTILs making photostability another important issue to be discussed. Finally, characteristic heterogeneities can be associated with specific physicochemical properties. Influencing these properties by adding conventional solvents, like water, can open a wide field of application, which is briefly summarized.

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“…In recent years, MD simulations have developed into a powerful tool for detailed studies on the structure and dynamics of ILs [18][19][20][21][22][23]. All-atom (AA) models not only revealed structural [20] and dynamical [18,[24][25][26] heterogeneity, but also yielded insights into their interplay [27,28]. However, such detailed atomistic modeling has also shortcomings.…”

Section: Introductionmentioning

confidence: 99%

Coarse-grained model of a nanoscale-segregated ionic liquid for simulations of low-temperature structure and dynamics

Kloth

Bernhardt

Vegt

et al. 2021

J. Phys.: Condens. Matter

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We perform molecular dynamics simulations to study the structure and dynamics of the ionic liquid [Omim][TFSI] in a broad temperature range. A particular focus is the progressing nanoscale segregation into polar and nonpolar regions upon cooling. As this analysis requires simulations of large systems for long times, we use the iterative Boltzmann inversion method to develop a new coarse-grained (CG) model from a successful all-atom (AA) model. We show that the properties are similar for both levels of description at room temperature, while the CG model shows stronger nanoscale segregation and faster diffusion dynamics than its AA counterpart at low temperatures. Exploiting these features of the CG model, we find that the characteristic length scale of the structural inhomogeneity nearly doubles to ∼3 nm when the temperature is decreased to about 200 K. Moreover, we observe that the nanoscale segregation is characterized by a bicontinuous morphology. In worm-like nonpolar regions, the ends of the octyl rests of the cations preferentially aggregate in the centers, while the other parts of the alkyl chains tend to be aligned parallel on a next-neighbor level and point outward, allowing for an integration of the imidazolium head groups of the cations into polar regions together with the anions, resembling to some degree the molecular arrangement in cylindrical micelles.

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Communication: Probing the existence of partially arrested states in ionic liquids

Cited by 17 publications

References 37 publications

Role of Dynamic Heterogeneities in Ionic Liquids: Insights from All‐Atom and Coarse‐Grained Molecular Dynamics Simulation Studies

Role of Dynamic Heterogeneities in Ionic Liquids: Insights from All‐Atom and Coarse‐Grained Molecular Dynamics Simulation Studies

Understanding the Photoexcitation of Room Temperature Ionic Liquids

Coarse-grained model of a nanoscale-segregated ionic liquid for simulations of low-temperature structure and dynamics

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