Polarization versus Temperature in Pyridinium Ionic Liquids

Many applications in chemistry, biology, and energy storage/conversion research rely on molecular simulations to provide fundamental insight into structural and transport properties of materials with high ionic concentrations. Whether the system is comprised entirely of ions, like ionic liquids, or is a mixture of a polar solvent with a salt, e.g., liquid electrolytes for battery applications, the presence of ions in these materials results in strong local electric fields polarizing solvent molecules and large ions. To predict properties of such systems from molecular simulations often requires either explicit or mean-field inclusion of the influence of polarization on electrostatic interactions. In this manuscript, we review the pros and cons of different treatments of polarization ranging from the mean-field approaches to the most popular explicit polarization models in molecular dynamics simulations of ionic materials. For each method, we discuss their advantages and disadvantages and emphasize key assumptions as well as their adjustable parameters. Strategies for the development of polarizable models are presented with a specific focus on extracting atomic polarizabilities. Finally, we compare simulations using polarizable and nonpolarizable models for several classes of ionic systems, discussing the underlying physics that each approach includes or ignores, implications for implementation and computational efficiency, and the accuracy of properties predicted by these methods compared to experiments.

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“…However, the molecular dipole moments increased as a function of temperature due to growing thermal fluctuations. 375…”

Section: Comparative Case Studiesmentioning

confidence: 99%

“…44 Interestingly, a temperature effect on the charge scaling factor derived by ESP charges could not be observed for simple molten salts 374 and pyridinium-based ionic liquids. 375…”

Section: Comparative Case Studiesmentioning

confidence: 99%

Molecular Dynamics Simulations of Ionic Liquids and Electrolytes Using Polarizable Force Fields

et al. 2019

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“…Ionic liquids and their mixtures with molecular liquids constitute a vibrant and currently very active research field. 1,[7][8][9][10] Ions in crystal lattices of purely ionic compounds are spherical. However, if the positive ion is sufficiently small and highly charged, it distorts the electron cloud of the negative ion.…”

Section: Introductionmentioning

confidence: 99%

Nonadditivity of Temperature Dependent Interactions in Inorganic Ionic Clusters

Chaban

Prezhdo

2015

J. Phys. Chem. C

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Nonadditivity of interactions implies, in the chemical context, that binding of atoms cannot be fully predicted from interactions between atom pairs. This phenomenon determines the identity of our world, which would have been much poorer otherwise. Ionic systems provide a good example of the interaction nonadditivity, which arises in most cases due to electron transfer and delocalization effects. Using Born−Oppenheimer molecular dynamics simulations of LiCl, NaCl, and KCl at 300, 1500, and 2000 K, we show that interaction nonadditivity originates from interplay of thermal motion and cation nature. In the case of alkali cations, ionic nature plays a more significant role than thermal effects. The nonadditivity is significant in all systems and at all temperatures considered. Dipole moments increase at higher temperatures due to thermal fluctuations and thermal expansion of the clusters. At the same time, ionic charges change little. Our results contribute to the fundamental understanding of electronic effects in nanoscale and condensed phase ionic systems, and foster progress in physical chemistry and engineering.

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“…This is also the case in imidazolium-and pyridinium-based RTILs. 12,31,32 Indeed, this group appears nearly neutral. For this reason, longer hydrocarbon chains can be avoided in simulaion, in order to save computational resources.…”

Section: Resultsmentioning

confidence: 96%

Are Fluorination and Chlorination of Morpholinium-Based Ionic Liquids Favorable?

Chaban

Prezhdo

2015

J. Phys. Chem. B

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Room-temperature ionic liquids (RTILs) constitute a fine-tunable class of compounds. Morpholinium-based cations are new to the field. They are promising candidates for electrochemistry, micellization, and catalytic applications. We investigate halogenation (fluorination and chlorination) of the N-ethyl-N-methylmorpholinium cation from the thermodynamics perspective. We find that substitutional fluorination is much more energetically favorable than substitutional chlorination, although the latter is also a permitted process. Although all halogenations at different locations are possible, they are not equally favorable. Furthermore, the trends are not identical in the case of fluorination and chlorination. We link the thermodynamic observables to electron density distribution within the investigated cation. The reported insights are based on the coupled-cluster technique, which is a highly accurate and reliable electron-correlation method. Novel derivatives of the morpholinium-based RTILs are discussed, motivating further efforts in synthetic chemistry.

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Polarization versus Temperature in Pyridinium Ionic Liquids

Cited by 14 publications

References 30 publications

Molecular Dynamics Simulations of Ionic Liquids and Electrolytes Using Polarizable Force Fields

Molecular Dynamics Simulations of Ionic Liquids and Electrolytes Using Polarizable Force Fields

Nonadditivity of Temperature Dependent Interactions in Inorganic Ionic Clusters

Are Fluorination and Chlorination of Morpholinium-Based Ionic Liquids Favorable?

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