As an expert in materials science, I have a deep understanding of the properties and behaviors of various materials. Glass, in particular, has been a fascinating subject of study due to its unique combination of transparency, rigidity, and brittleness. The question of the hardest glass to break is not just about the material's resistance to physical impact but also about its chemical composition, structure, and the manufacturing process.

Introduction to Glass
Glass is an amorphous solid material that is typically transparent and has widespread practical, technological, and decorative usage due to its aesthetic properties. It is made by heating a mixture of sand (silica), soda (sodium carbonate), and lime (calcium oxide) to a high temperature and rapidly cooling it to retain a disordered atomic structure.

The Challenge of Glass Strength
Traditionally, glass is known for its brittleness and susceptibility to breaking. However, advancements in material science have led to the development of various types of glass that exhibit enhanced strength and durability. The strength of glass can be improved through chemical strengthening, where ions are exchanged in the glass surface to create a layer of compressed material, making it more resistant to breaking.

New Metallic Glass
Recent developments have introduced a new category of glass that is incredibly tough and strong. This is known as metallic glass, and it is made from a mixture of metals, often including palladium and other elements. The unique atomic structure of metallic glass provides it with exceptional mechanical properties.

Properties of Metallic Glass
The palladium-based metallic glass, mentioned in the reference material, is particularly noteworthy. It has an amorphous structure that lacks the grain boundaries found in crystalline materials, which are often the sites of crack initiation and propagation. This lack of grain boundaries contributes to the material's high toughness and strength.

Resistance to Cracking
When subjected to stress, the palladium-based metallic glass is observed to bend before it breaks. This is a significant property because it allows the material to absorb and distribute stress more effectively, reducing the likelihood of catastrophic failure. The initial sharp crack that might form in the material is less likely to propagate due to the material's ability to deform plastically, which is a characteristic not commonly found in traditional glass.

Manufacturing and Applications
The manufacturing process of metallic glass is complex and requires precise control of cooling rates and composition. This material is finding applications in various fields where high strength and durability are required, such as in aerospace, automotive, and electronics industries.

Conclusion
In conclusion, the hardest glass to break, based on current scientific understanding and material advancements, would be a type of metallic glass, specifically palladium-based. Its unique atomic structure and ability to deform plastically under stress make it exceptionally resistant to breaking. While traditional glass remains brittle, the innovation in metallic glass represents a significant leap forward in material science, offering new possibilities for applications where extreme strength and durability are paramount.

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New Metallic Glass Beats Steel as the Toughest, Strongest Material Yet. An initial sharp crack in palladium-based metallic glass causes the material to bend before it breaks.Jan 11, 2011read more >>