Influence of impurities on two-level systems in amorphous ice

Journal of Non-Crystalline Solids, 2006

Based on neutron wide-angle diffraction and small-angle neutron scattering experiments, we show that there is a correlation between the preparational conditions of amorphous ice structures, their microscopic structural properties, the extent of heterogeneities on a mesoscopic spatial scale and the transformation kinetics. There are only two modifications that can be identified as homogeneous disordered structures, namely the very high-density vHDA and the low-density amorphous LDA ice. Structures showing an intermediate static structure factor with respect to vHDA and LDA are heterogeneous phases. This holds independently from their preparation procedure, i.e. either obtained by pressure amorphisation of ice I h or by heating of vHDA. The degree of heterogeneity can be progressively suppressed when higher pressures and temperatures are applied for the sample preparation. In accordance with the suppressed heterogeneity the maximum of the static structure factor displays a pronounced narrowing of the first strong peak, shifting towards higher Qnumbers. Moreover, the less heterogeneous the obtained structures are the slower is the transformation kinetics from the high-density modifications into LDA. The well known high-density amorphous structure HDA does not constitute any particular state of the amorphous water network. It is formed due to the preparational procedure working in liquid nitrogen as thermal bath, i.e. at about 77 K.

Journal of Physics: Condensed Matter, 2003

Careful neutron diffraction measurements on deuterated low density amorphous (LDA) ice confirm that at 120 K it can be considered a fully 'annealed' structure, as no significant changes are observed in the amorphous spectra until crystallization occurred over time at 130 K. On this basis, the measurement of structural differences between the hydrogenated and deuterated forms of LDA ice at 120 K, have been carried out using 98 keV electromagnetic radiation diffraction techniques. The maximum observed isotope effect in LDA ice is ∼3.4% at 40 K when compared to the magnitude of the first peak in the electronic structure factor at Q = 1.70 Å −1 . This compares to a maximum effect of ∼1.6% previously measured in liquid water at room temperature (Tomberli et al 2000 J. Phys.: Condens. Matter. 12 2597). The isotope effect is shown to be similar to a temperature shift in the structure of light LDA ice. However, the existence of a first sharp diffraction peak at Q = 1.0 Å −1 in the isotopic difference function is not reproduced in the temperature difference and suggests that additional longer-range correlations are present in the more ordered deuterated form.

Physical Review Materials, 2018

The Journal of Physical Chemistry Letters

High-density (HDA) and low-density amorphous ices (LDA) are believed to be counterparts of the high-and low-density liquid phases of water, respectively. In order to better understand how the vibrational modes change during the transition between the two solid states, we present infrared spectroscopy measurements, following the change of the decoupled OD-stretch (v OD) (∼2460 cm −1) and OH-combinational mode (v OH + v 2 , v OH + 2v R) (∼5000 cm −1). We observe a redshift from HDA to LDA, accompanied with a drastic decrease of the bandwidth. The hydrogen bonds are stronger in LDA, which is caused by a change in the coordination number and number of water molecules interstitial between the first and second hydration shell. The unusually broad uncoupled OD band also clearly distinguishes HDA from other crystalline high-pressure phases, while the shape and position of the in situ prepared LDA are comparable to those of vapor-deposited amorphous ice.

Applied Physics A: Materials Science & Processing, 2002

Proceedings of The National Academy of Sciences, 2009

Polymorphism of water has been extensively studied, but controversy still exists over the phase transition between high-density amorphous (HDA) and low-density amorphous (LDA) ice. We report the phase behavior of HDA ice inside high-pressure cryocooled protein crystals. Using X-ray diffraction, we demonstrate that the intermediate states in the temperature range from 80 to 170 K can be reconstructed as a linear combination of HDA and LDA ice, suggesting a first-order transition. We found evidence for a liquid state of water during the ice transition based on the protein crystallographic data. These observations open the possibility that the HDA ice induced by high-pressure cryocooling is a genuine glassy form of high-density liquid.

Physical Review Letters, 2017

The Journal of Physical Chemistry Letters, 2013

Despite the importance of low-density amorphous ice (LDA) in critical cosmological processes and its prominence as one of the polyamorphs of water there is still an incomplete picture of the processes that take place upon thermal annealing. Using Raman and Fourier transform infrared (FT-IR) spectroscopy, we show that a gradual structural relaxation process takes place upon heating vapor-deposited LDA, also called amorphous solid water, and LDAs obtained from several different states of high-density amorphous ice. The relaxation leads to an increase in structural order on local and more extended length scales as the average O−O distance shortens and the O−O distance distribution narrows. The relaxation process is separate from crystallization, and it does not seem to reach completion before crystallization sets in. Our findings are difficult to reconcile with the postulated glass transition of LDA to the supercooled and highly viscous liquid prior to crystallization.

Proceedings of the National Academy of Sciences of the United States of America, 2017

Water exists in high- and low-density amorphous ice forms (HDA and LDA), which could correspond to the glassy states of high- (HDL) and low-density liquid (LDL) in the metastable part of the phase diagram. However, the nature of both the glass transition and the high-to-low-density transition are debated and new experimental evidence is needed. Here we combine wide-angle X-ray scattering (WAXS) with X-ray photon-correlation spectroscopy (XPCS) in the small-angle X-ray scattering (SAXS) geometry to probe both the structural and dynamical properties during the high-to-low-density transition in amorphous ice at 1 bar. By analyzing the structure factor and the radial distribution function, the coexistence of two structurally distinct domains is observed at T = 125 K. XPCS probes the dynamics in momentum space, which in the SAXS geometry reflects structural relaxation on the nanometer length scale. The dynamics of HDA are characterized by a slow component with a large time constant, aris...

The Journal of Physical Chemistry B, 2002

High-density amorphous ice (HDA), made by compression of hexagonal ice at 77 K, was heated at a constant pressure of 0.81 GPa up to 195 K and its phase transition followed by displacement-temperature curves. The crystalline phases recovered at 77 K and 1 bar were characterized by X-ray diffraction. Pure D 2 O ice IV and nearly pure H 2 O ice IV were formed on slow heating at a rate of ≈0.4 K min -1 , whereas pure H 2 O and D 2 O ice XII were formed on fast heating at g15 K min -1 . On heating HDA at rates inbetween, a mixture of ice IV and ice XII is obtained, where their relative yields depend in a systematic manner on the heating rate. Conversion of HDA into either ice IV or ice XII is an example of a "parallel reaction" where the relative yields of ice IV and ice XII can be controlled by temperature, that is in our approach by the rate of heating. It is conceivable that a similar behavior occurs on crystallization of the related pressure-amorphized silica.