Polyamorphism and liquid-liquid phase transitions: challenges for experiment and theory

MCMILLAN, Paul F., WILSON, Mark, WILDING, Martin, DAISENBERGER, Dominik, MEZOUAR, Mohamed and GREAVES, G. Neville (2007). Polyamorphism and liquid-liquid phase transitions: challenges for experiment and theory. Journal of Physics: Condensed Matter, 19 (41), p. 415101.

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Official URL: http://iopscience.iop.org/article/10.1088/0953-898...
Link to published version:: https://doi.org/10.1088/0953-8984/19/41/415101

Abstract

Phase transitions in the liquid state can be related to pressure-driven fluctuations developed in the density (i.e., the inverse of the molar volume; ρ = 1/V) or the entropy (S(T)) rather than by gradients in the chemical potential (μ(X), where X is the chemical composition). Experiments and liquid simulation studies now show that such transitions are likely to exist within systems with a wide range of chemical bonding types. The observations permit us to complete the trilogy of expected liquid state responses to changes in P and T as well as μ(X), as is the case among crystalline solids. Large structure–property changes occurring within non-ergodic amorphous solids as a function of P and T are also observed, that are generally termed 'polyamorphism'. The polyamorphic changes can map on to underlying density- or entropy-driven L–L transitions. Studying these phenomena poses challenges to experimental studies and liquid simulations. Experiments must be carried out over a wide P–T range for in situ structure–property determinations, often in a highly metastable regime. It is expected that L–L transitions often occur below the melting line, so that studies encounter competing crystallization phenomena. Simulation studies of liquid state polyamorphism must involve large system sizes, and examine system behaviour at low T into the deeply supercooled regime, with distance and timescales long enough to sample characteristic density/entropy fluctuations. These conditions must be achieved for systems with different bonding environments, that can change abruptly across the polyamorphic transitions. Here we discuss opportunities for future work using simulations combined with neutron and x-ray amorphous scattering techniques, with special reference to the behaviour of two polyamorphic systems: amorphous Si and supercooled Y2O3–Al2O3 liquids.

Item Type: Article
Additional Information: International Workshop on Current Challenges in Liquid and Glass Science, Abingdon, ENGLAND, JAN 10-12, 2007
Research Institute, Centre or Group - Does NOT include content added after October 2018: Materials and Engineering Research Institute > Engineering Research
Departments - Does NOT include content added after October 2018: Faculty of Science, Technology and Arts > Department of Engineering and Mathematics
Identification Number: https://doi.org/10.1088/0953-8984/19/41/415101
Depositing User: Martin Wilding
Date Deposited: 04 Jul 2018 09:13
Last Modified: 04 Jul 2018 09:13
URI: http://shura.shu.ac.uk/id/eprint/21502

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