Ice VII from aqueous salt solutions: From a glass to a crystal with broken H-bonds

• Published in: Scientific reports Vol. 6; no. 1; p. 32040
• Main Authors: Klotz, S., Komatsu, K., Pietrucci, F., Kagi, H., Ludl, A.-A., Machida, S., Hattori, T., Sano-Furukawa, A., Bove, L. E.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 26.08.2016; Nature Publishing Group
• Subjects: 119/118; 639/301/119/2795; 639/638/440/94; Aqueous solutions; Condensed Matter; Decompression; Diffraction; Humanities and Social Sciences; Ice; Lithium chloride; multidisciplinary; Neutron diffraction; Periodicity; Physics; Pressure; Science; Translation
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/srep32040

It has been known for decades that certain aqueous salt solutions of LiCl and LiBr readily form glasses when cooled to below ≈160 K. This fact has recently been exploited to produce a « salty » high-pressure ice form: When the glass is compressed at low temperatures to pressures higher than 4 GPa and subsequently warmed, it crystallizes into ice VII with the ionic species trapped inside the ice lattice. Here we report the extreme limit of salt incorporation into ice VII, using high pressure neutron diffraction and molecular dynamics simulations. We show that high-pressure crystallisation of aqueous solutions of LiCl∙RH 2 O and LiBr∙RH 2 O with R = 5.6 leads to solids with strongly expanded volume, a destruction of the hydrogen-bond network with an isotropic distribution of water-dipole moments, as well as a crystal-to-amorphous transition on decompression. This highly unusual behaviour constitutes an interesting pathway from a glass to a crystal where translational periodicity is restored but the rotational degrees of freedom remaining completely random.