# Anisotropic Dielectric Relaxation in Single Crystal H$_{2}$O Ice Ih from 80-250 K

## TL;DR

This study investigates the dielectric relaxation properties of ultra-pure single crystal ice Ih across 80-250 K, revealing anisotropic molecular reorientations and their relation to proton ordering and defect dynamics.

## Contribution

It provides new insights into the anisotropic dielectric relaxation mechanisms and their connection to proton ordering in ice Ih at low temperatures.

## Key findings

- Relaxation dominated by Bjerrum defects below 140 K.
- Molecular reorientations along the c-axis are energetically favored.
- Supports a link between dielectric relaxation and proton ordering near 100 K.

## Abstract

Three properties of the dielectric relaxation in ultra-pure single crystalline H$_{2}$O ice Ih were probed at temperatures between 80-250 K; the thermally stimulated depolarization current, static electrical conductivity, and dielectric relaxation time. The measurements were made with a guarded parallel-plate capacitor constructed of fused quartz with Au electrodes. The data agree with relaxation-based models and provide for the determination of activation energies, which suggest that relaxation in ice is dominated by Bjerrum defects below 140 K. Furthermore, anisotropy in the dielectric relaxation data reveals that molecular reorientations along the crystallographic $c$-axis are energetically favored over those along the $a$-axis between 80-140 K. These results lend support for the postulate of a shared origin between the dielectric relaxation dynamics and the thermodynamic partial proton-ordering in ice near 100 K, and suggest a preference for ordering along the $c$-axis.