Dielectric and Transport Properties of Acetonitrile at Varying Temperatures: a Molecular Dynamics Study

Abstract

Use of acetonitrile in electrolytes promotes better operation of supercapacitors. Recent efforts show that electrolytes containing acetonitrile can also function in a wide range of operating temperatures. Therefore, this paper addresses the dielectric relaxation processes, structure and dynamic properties of the bulk acetonitrile at various temperatures. Systems of acetonitrile were modeled using canonical ensemble and simulated by employing Molecular Dynamics method. Results show that interactions among the molecules were correlated within a cut-off radius while parallel and anti-parallel arrangements are observed beyond this radius at relatively high and low temperatures respectively. Furthermore, effects of C-C-N and C-H bending modes were greatly appreciated on the power spectral density of time rate change of dipole-dipole correlations whereas frequency shifts were observed on all modes at the lowest temperature under consideration. Linear variations with temperature were depicted for reorientation times and self-diffusion coefficients. Shear viscosity was also computed with a good accuracy within a certain range of the temperature as well.

Effect of proximity to ionic liquid-solvent demixing on electrical double layers

“…where β = 1/(k B T ), u is the electrostatic potential in k B T /e units with k B denoting the Boltzmann constant; c = ρ + − ρ − is the charge density per elementary charge e and λ B = βe 2 /ǫ is the Bjerrum length, where ǫ is the dielectric constant. It is well known that ǫ depends on temperature, particularly for polar solvents [33][34][35]. Nevertheless, we assume ǫ to be temperature-independent, and note that its temperature variation should not affect the results qualitatively, as pointed out in [30].…”

Systematic evaluation and refinement of existing all‐atom force fields for the simulation of liquid acetonitrile

“…So far, numerous studies have been devoted to the experimental investigation of various aspects of ACN properties by means of diverse techniques such as X‐ray, neutron‐diffraction, IR spectroscopy, and 1 H NMR at the pure liquid state and mixtures with other compounds . Besides, many theoretical studies have achieved valuable physicochemical and structural insights into systems involving ACN through MD simulations . For example, our previous MD simulation study focused on the quantitative and qualitative investigation of the dynamical behavior and microscopic structural properties of IL 1‐hexyl‐2,3‐dimethylimidazolium bis(fluorosulfonyl)imide ([C 6 mmim][FSI]) in the pure state and its binary mixtures with ACN.…”

“…In this way, the success of the molecular simulation study strongly related to the quality/precision of applied potential functions. The force fields proposed for ACN are divided into two categories: the simple (rigid) three‐site model where a single interaction site is considered for the methyl group (united‐atom force field), and the more explicit (flexible) six‐site model in which carbon and three hydrogen atoms attached to it act as separated interaction sites (all‐atom force field) . Systematic evaluation and comparison of some available three‐site models of liquid ACN have previously been presented .…”

“…In another MD study, Orhan (in 2014) designed a new six‐site model for ACN which was adopted from DREIDING/A force field with some minor changes. The dielectric relaxation processes, structure, vibrational spectra, dynamics, and transport properties of bulk ACN were successfully addressed at different temperatures.…”

“…Here, we test the capability of Orhan's model in the prediction of self‐diffusion and thermodynamic properties (see below). However, its ability in the prediction of the thermodynamic properties of ACN was not studied in the validation stage of the original report …”