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Pressure-induced polyamorphism in salty water
L E Bove1, S Klotz, J Philippe
1IMPMC, CNRS-UMR 7590, Université P&M Curie, 75252 Paris, France.
Physical Review Letters
|April 27, 2011
Summary
High pressure and low temperature induce a reversible transformation in lithium chloride (LiCl) solutions, forming a new high-density amorphous state. This polyamorphic transition involves structural changes in water molecules around lithium ions.
Area of Science:
- Physical Chemistry
- Materials Science
- Condensed Matter Physics
Background:
- Ionic salt aqueous solutions exhibit complex phase behavior under varying conditions.
- Understanding metastable states is crucial for materials science and chemistry.
- Lithium chloride (LiCl) solutions are model systems for studying hydration and phase transitions.
Purpose of the Study:
- To investigate the metastable phase diagram of LiCl:6D₂O at high pressure and low temperature.
- To characterize the transformation to a high-density amorphous (HDA) phase.
- To elucidate the structural mechanisms driving the polyamorphic transition.
Main Methods:
- Neutron diffraction measurements were employed to probe the structure.
- Advanced computer simulations were utilized to model the system's behavior.
- Annealing under high pressure and low temperature conditions were performed.
Main Results:
- A stepwise transformation to a very high-density amorphous form was observed.
- The transition is abrupt, occurring at 120 K and 2 GPa.
- The transition is reversible and accompanied by a significant enthalpy release.
Conclusions:
- The presence of LiCl salt induces a polyamorphic transition in the aqueous solution.
- Simulations indicate a local structural reorganization of water around Li ions drives the transition.
- This study reveals a novel high-density amorphous state in LiCl:6D₂O solutions.
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