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Article by: Andacs Robert Eugen, on 16 August 2023, at 03:12 am PDT

Substances made of plastic or glass fall under amorphous materials, which resist the process of crystallization even when temperatures drop. Despite being called "solids," materials like plastic and glass have a slow flow characteristic of supercooled liquids.

Scientists have long been puzzled by the microstructural transformation of these materials into solid form. Still, researchers from the Department of Energy's Lawrence Berkeley National Laboratory have discovered hidden intricacies governing molecular actions within supercooled liquids. This breakthrough has led to a better understanding of the phase change between liquid and solid states, with the potential for creating innovative amorphous materials for medical implements, drug dispersion, and other uses.

Combining theory, computational simulations, and experimental observations, the team uncovered the molecular choreography that occurs as materials approach a threshold temperature known as the "onset temperature." At this point, viscosity increases, and the material becomes more solid-like, marking the beginning of rigidity. This metamorphosis is what separates supercooled fluids from other substances.

"Our theory predicts the onset temperature measured in model systems and explains why the behavior of supercooled liquids around that temperature is reminiscent of solids even though their structure is the same as that of the liquid," said the author of this work, Kranthi Mandadapu, a staff scientist in Berkeley Lab's Chemical Sciences Division and professor of chemical engineering at the University of California, Berkeley.

This information is based on a theory that combines existing knowledge with new ideas. According to this theory, the molecules in a 2D supercooled liquid move similarly to the defects found in crystalline structures.

As the temperature rises towards a certain point, the previously joined defects dissolve and become singular entities. This causes a significant shift in the material, making it less rigid and more like a typical liquid.

The temperature at which this transformation occurs is similar to the melting point of other materials. This concept applies to various supercooled fluids and glassy configurations, creating a unified understanding.

The molecular ensemble of a supercooled liquid is constantly changing, resulting in localized tremors called "excitations." This theory expands on the metaphorical journey of a 2D supercooled drink, envisioning a path filled with excitation similar to the fissures in crystalline structures.

The researchers looked at the horizon, dreaming of expanding their model to include 3D systems. This development would transform their intricate framework into a three-dimensional symphony, unraveling the complex interplay between localized gestures and neighboring excitations. This orchestration ultimately leads to the wholesale relaxation of the liquid ensemble. By harmonizing a mosaic of diverse elements, the researchers hope to create a comprehensive and cohesive portrait of the emergence of glassy dynamics aligned with modern-day observation.

Mandadapu and his colleagues aspire to transfer these findings into three-dimensional structures. Additionally, they intend to examine the intricacies governing the transition of localized gestures into proximate excitations. This underscores the integration of diverse elements, resulting in a holistic representation that aligns with modern-day observation.

The contrast between supercooled liquids and their animated, high-temperature counterparts is intriguing. The vista unraveled delves into the heart of this enigma, much like a tapestry unveiling layer after layer. The complex weave spun by these beguiling states of matter beckons the keenest minds to decipher it.

"It's fascinating from a basic science point of view to examine why these supercooled liquids exhibit remarkably different dynamics than the regular liquids that we know," said Mandadapu.