Following the Crystallization of Amorphous Ice after Ultrafast Laser Heating

Abstract

Using time-resolved wide-angle X-ray scattering, we investigated the early stages (10 μs–1 ms) of crystallization of supercooled water, obtained by the ultrafast heating of high- and low-density amorphous ice (HDA and LDA) up to a temperature T = 205 K ± 10 K. We have determined that the crystallizing phase is stacking disordered ice ( I sd ), with a maximum cubicity of χ = 0.6, in agreement with predictions from molecular dynamics simulations at similar temperatures. However, we note that a growing small portion of hexagonal ice ( I h ) was also observed, suggesting that within our timeframe, I sd starts annealing into I h . The onset of crystallization, in both amorphous ice, occurs at a similar temperature, but the observed final crystalline fraction in the LDA sample is considerably lower than that in the HDA sample. We attribute this discrepancy to the thickness difference between the two samples.

Infrared Spectroscopy on Equilibrated High-Density Amorphous Ice

“…We relate this to the so-called stacking disordered ice (Isd) formation, which has a slightly different OD-stretch vibrational frequency than hexagonal ice . Formation of Isd from heating LDA or ASW was already reported in several works ,,− and is consistent with recent X-ray data taken at such grid samples . We here find a O–O distance for ice Isd of R = 2.755 Å.…”

“… 54 Formation of Isd from heating LDA or ASW was already reported in several works 18 , 39 , 53 − 55 and is consistent with recent X-ray data taken at such grid samples. 58 We here find a O–O distance for ice Isd of R = 2.755 Å. This is, we observe eHDA to be stable in the range 80–115 K as well sa LDA in the range 125–140 K and observe crystallization at 150 K.…”

Using coherent X-rays to follow dynamics in amorphous ices

“…The HDA to LDA transformation was followed by crystallization to a stacking disordered crystalline ice as expected from both experiments and simulations of the early stages of crystallisation at ambient pressure. 42,43…”

“…The HDA to LDA transformation was followed by crystallization to a stacking disordered crystalline ice as expected from both experiments and simulations of the early stages of crystallisation at ambient pressure. 42,43 3.1.2 Structural transformation during slow heating, accompanied by dynamical investigations. XPCS is used to investigate the molecular dynamics at different selected temperatures throughout the transition from HDA to LDA.…”

“…The ice then forms a stacking disordered ice I sd with high cubicity. 42,43 This nding might have an impact on understanding crystallization from amorphous ice in summer-mesospheric clouds, 8 as also the mm-sized ice layer resembles a more realistic model system.…”