Molecular-level evaluation of ionic transport under external electric fields in biological dielectric liquids

LY Dan and K Zhang and ZY Huang and FP Wang and Q Wang and J Li, JOURNAL OF MOLECULAR LIQUIDS, 340, 116883 (2021).

DOI: 10.1016/j.molliq.2021.116883

Ionic conduction is a critical parameter to evaluate the electrical performance of biological dielectric liquids. In this work, detailed molecular dynamics (MD) simulations were carried out to reveal both drift mechanisms of ions (H3O+, Cu2+, OH- and Cl-) and local structure evolution characteristics in biological dielectric liquids under external electric fields. The drift velocities of all ionic species increase nonlinearly with the addition of static electric fields. At relatively low field regimes, the structural cages formed by corresponding biological dielectric molecules are found to reduce ion transport. Above certain field thresholds, the accelerated ions impart appreciable energy to the surrounding molecular segments, making the binding of the cages broken. As such, the electric motion as a replacement of the thermal motion is eventually taken place. The computed thresholds are 0.97 V/nm, 0.645 V/nm, 0.67 V/nm, and 0.77 V/nm for H3O+, Cu2+, OH- and Cl(- )respectively. Additionally, given the electrostatic potential feature of biological dielectric molecules, the structural cages have greater advantages in limiting cationic migration, in which the binding effect for cations is more stable and persistent. The results provide a helpful guideline for designing the next- generation biological dielectric liquids. (C) 2021 Elsevier B.V. All rights reserved.

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