Medium-density amorphous ice unveils shear rate as a new dimension in water’s phase diagram

What is it about?

This study explores intriguing questions about the nature of a newly discovered form of ice, medium-density amorphous ice (MDA), and its role in the complex phase behavior of water. Using molecular simulations, the authors reveal that, unlike other amorphous ices, MDA is a completely distinct phase formed through the application of shear forces. This discovery highlights shear rate as a critical factor in water's phase diagram, making MDA unique among non-crystalline states of water. By demonstrating that shear forces can transform water’s structure in ways temperature and pressure alone cannot, the research provides new insights into water’s behavior and opens up pathways to access new states of matter with distinct properties.

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Photo by beau mori on Unsplash

Photo by beau mori on Unsplash

Why is it important?

This study offers a groundbreaking perspective on water's behavior under extreme conditions, adding a new dimension to its already complex phase diagram. By uncovering how shear forces create a new class of amorphous ice, medium-density amorphous ice (MDA), it emphasizes the previously unexplored role of mechanical forces in shaping water’s structure. The findings establish MDA as a distinct phase, different from other amorphous ices and liquid water, while also providing valuable insights into the behavior of similar materials, such as silicon and silica. By investigating how amorphous phases are formed through shearing, this research opens new avenues for designing materials with tunable properties. Key takeaways: • The study identifies MDA as a distinct form of amorphous ice, formed by applying shear forces to ice. It is different from the previously known low-density (LDA) and high-density amorphous (HDA) ices, occupying a unique position in water's phase diagram. • The research introduces shear rate as a critical thermodynamic variable that drives the formation of distinct amorphous phases. It reveals that shear forces enable access to a continuum of amorphous states of water that cannot be achieved by manipulating temperature and pressure alone. • The study highlights that MDA, as a shear-driven phase, is a non-equilibrium state with properties dependent on pressure, temperature, and shear rate. It provides a deeper understanding of how amorphous phases form, transform, and behave under extreme conditions. • The findings extend beyond water, providing insights into other tetrahedral materials like silicon and silica. The research suggests that mechanical forces could play a crucial role in the formation and stability of non-crystalline materials.