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About this book

Christina Maria Tonauer finds novel evidence for the first-order nature of the transition between high-density amorphous ice (HDA) and low-density amorphous ice (LDA), supporting water’s liquid-liquid transition scenarios. Pressure-dependent crystallisation experiments of differently prepared expanded high-density amorphous ice samples (eHDA) and subsequent powder x-ray diffraction experiments disclose nucleation of LDA domains in bulk HDA, a typical feature of a first-order transition. The comparison of pressure-dependent crystallisation temperatures of eHDA samples with LDA nuclei and bulk LDA allows the estimation of the Laplace pressure and the size of a LDA nucleus.

Table of Contents

Frontmatter

Chapter 1. Introduction

Abstract
Being vital for all known forms of life on Earth, the significance of water has manifested in all cultural fields, e. g., philosophy, religion, art, music, and obviously, science. The origins of water’s modern scientific exploration date back to the 17th century [1]. At that time Kepler recognised the perfect sixfold symmetry of snowflakes to be a result of the microscopic structure of the constituent particles [2–4].
Christina Maria Tonauer

Chapter 2. Methods

Abstract
Dilatometric methods enable the measurement of variations of a dimension (length) of a sample, for example as a function of temperature. Volume changes of samples upon temperature changes can, therefore, be easily calculated. In the present setup (see section 2.1.1) the measurement of length variations as a function of pressure is also possible. According to (Equ. 04) and (Equ. 05), the slopes of the volume curves ΔV(p) (in an isothermal experiment) and ΔV(T) (in an isobaric experiment) are a direct measure for a sample’s isothermal compressibility κT and thermal expansion coefficient α, respectively.
Christina Maria Tonauer

Chapter 3. Experimental section [167]

Abstract
In Fig. 13, the first step is depicted by the horizontal arrow with a grey arrowhead. Hexagonal ice (big turquoise hexagon) is compressed from atmospheric pressure to 1.6 GPa. Following in essence the protocol by Mishima et al. [26], subsequently, decompression to 1.1 GPa is performed (T ~ 77 K; compression/decompression rate: 0.1 GPa min−1).
Christina Maria Tonauer

Chapter 4. Discussion [167]

Abstract
Based on the crystallisation line Tx(p) of eHDA0.2 and eHDA0.3 in Fig. 26 (a), as well as the analysis of the resulting crystallisation products in Fig. 27 (b), no significant difference between the nature of eHDA0.2 and eHDA0.3 is assumed, neither in the thermal stability against crystallisation nor in the crystallisation mode, as both starting materials yield similar crystallisation products. The presence of one main crystalline phase (and only marginal amounts of another phase) after crystallisation indicates that both, eHDA0.2 and eHDA0.3, can be regarded glassy, in other words the low-temperature proxy of HDL [101, 149, 152]. By contrast, the crystallisation line Tx(p) of eHDA0.1 exhibits quite different behaviour (see Fig. 26 (a)).
Christina Maria Tonauer

Chapter 5. Summary [166]

Abstract
The present thesis covers a study on the pressure dependence of the crystallisation temperature in eHDA samples of different preparation history. The crystallisation temperatures summarised in Fig. 26(a) show that different crystallisation modes are operative for different samples. This observation is rationalised with LDA-nanodomains forming in eHDA< 0.2.
Christina Maria Tonauer

Backmatter

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