Ice: An Impedance Spectroscopy and Atomistic Simulation Study.

摘要

As mankind approaches the cusp of deep space exploration in our quest to seek out new or similar forms of life, ice has experienced a resurgence of new research interests due to its omnipresence beyond Earth. Therefore, the search for life beyond our planet hinges on the understanding of planetary ice and its interactions with bio-precursors that could preserve indications of pre-existent life or currently capable of sustaining ecosystems suitable for life by providing nutrients in the form of chemical energy.;The dissertation manuscript investigates the electrical properties of ice using electrochemical impedance spectroscopy (EIS) and atomistic simulations in an effort to develop an unambiguous instrumentation platform for in-situ planetary exploration. The experimental portion of the work emphasized the electrical properties behavior of ices doped with ion in order to characterize unique the signatures from detectable from EIS measurements on different ionic species. To further delve into the transport properties of pure and ion doped ices at the molecular level, molecular dynamics simulations were also performed on KCl-doped ice under various temperature conditions and over a long simulation time of greater than 1 i-sec. The systems of atomistic simulations on ice included the addition of the electric field to mimic actual experimental conditions.;The experiment process also included the development of a unique electrode configuration suitable for long-life field applications. Measurement results on pure ice using this novel electrode configuration are in excellent agreement with measurements from baseline parallel plate electrodes. Resonance is also detected with the new configuration at the onset of the Debye relaxation which is unique to our measurement results. A database of ice measurements resulted in a substantial collection of ice electrical properties parameters suitable for ice characterization based on ionic species and concentration.;From simulations on pure and KCl-doped ices, structural and transport dynamics was characterized using RDF, MSD, and displacement profiles. In addition, the physical properties (e.g., density and heat capacity) of ice calculated from simulation are in agreement with actual ice indicating good simulation behavior and provide further validation of results. Comparison of the electrical properties from the simulations and the experiments indicated excellent agreement as well. Though many new finding were made regarding the dynamic behavior of ice, the core discovery from simulation is the motions of ions across adjacent ice cavities due to erratic jumps which enhance the observed transport properties. Such jump events were also substantiated by trajectory plots over the entire simulation time.