Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

When things get glassy, molecules go fractal

24.04.2014

Explaining the mysterious dynamics of glassy materials

Colorful church windows, beads on a necklace and many of our favorite plastics share something in common -- they all belong to a state of matter known as glasses. School children learn the difference between liquids and gases, but centuries of scholarship have failed to produce consensus about how to categorize glass.


The research confirmed that glasses form when their molecules get jammed into fractal 'wells,' as shown on the right, rather than smooth or slightly rough wells (left).

Credit: Patrick Charbonneau

Now, combining theory and numerical simulations, researchers have resolved an enduring question in the theory of glasses by showing that their energy landscapes are far rougher than previously believed. The findings appear April 24 in the journal Nature Communications.

"There have been beautiful mathematical models, but with sometimes tenuous connection to real, structural glasses. Now we have a model that's much closer to real glasses," said Patrick Charbonneau, one of the co-authors and assistant professor of chemistry and physics at Duke University.

The new model, which shows that molecules in glassy materials settle into a fractal hierarchy of states, unites mathematics, theory and several formerly disparate properties of glasses.

One thing that sets glasses apart from other phase transitions is a lack of order among their constituent molecules. Their cooled particles become increasingly sluggish until, caged in by their neighbors, the molecules cease to move -- but in no predictable arrangement. One way for researchers to visualize this is with an energy landscape, a map of all the possible configurations of the molecules in a system.

Charbonneau said a simple energy landscape of glasses can be imagined as a series of ponds or wells. When the water is high (the temperature is warmer), the particles within float around as they please, crossing from pond to pond without problem. But as you begin to lower the water level (by lowering the temperature or increasing the density), the particles become trapped in one of the small ponds. Eventually, as the pond empties, the molecules become jammed into disordered and rigid configurations.

"Jamming is what happens when you take sand and squeeze it," Charbonneau said. "First it's easy to squeeze, and then after a while it gets very hard, and eventually it becomes impossible."

Like the patterns of a lakebed revealed by drought, researchers have long wondered exactly what "shape" lies at the bottom of glass energy landscapes, where molecules jam. Previous theories have predicted the bottom of the basins might be smooth or a bit rough.

"At the bottom of these lakes or wells, what you find is variation in which particles have a force contact or bond," Charbonneau said. "So even though you start from a single configuration, as you go to the bottom or compress them, you get different realizations of which pairs of particles are actually in contact."

Charbonneau and his co-authors based in Paris and Rome showed, using computer simulations and numeric computations, that the glass molecules jam based on a fractal regime of wells within wells.

The new description makes sense of several behaviors seen in glasses, like the property known as avalanching, which describes a random rearrangement of molecules that leads to crystallization.

"There are a lot of properties of glasses that are not understood, and this finding has the potential to bring together a wide range of those problems into one coherent picture," said Charbonneau.

Understanding the structure of glasses is more than an intellectual exercise -- materials scientists stand to advance from the knowledge, which could lead to better control of the aging of glasses.

###

Co-authors on the paper included Jorge Kurchan and Pierfrancesco Urbani of Paris, and Giorgio Parisi and Francesco Zamponi of Rome.

This work was supported by the European Research Council (grants NPRGGLASS and #247328) and the Alfred P. Sloan Foundation.

Citation: "Fractal free energy landscapes in structural glasses," Patrick Charbonneau, Jorge Kurchan, Giorgio Parisi, et al. Nature Communications, April 24, 2014. DOI: 10.1038/ncomms4725.

Karl Bates | Eurek Alert!

Further reports about: glassy landscape landscapes liquids materials particles problems properties temperature

More articles from Materials Sciences:

nachricht Clay nanotube-biopolymer composite scaffolds for tissue engineering
02.05.2016 | Kazan Federal University

nachricht Personal cooling units on the horizon
29.04.2016 | Penn State

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Nuclear Pores Captured on Film

Using an ultra fast-scanning atomic force microscope, a team of researchers from the University of Basel has filmed “living” nuclear pore complexes at work for the first time. Nuclear pores are molecular machines that control the traffic entering or exiting the cell nucleus. In their article published in Nature Nanotechnology, the researchers explain how the passage of unwanted molecules is prevented by rapidly moving molecular “tentacles” inside the pore.

Using high-speed AFM, Roderick Lim, Argovia Professor at the Biozentrum and the Swiss Nanoscience Institute of the University of Basel, has not only directly...

Im Focus: 2+1 is Not Always 3 - In the microworld unity is not always strength

If a person pushes a broken-down car alone, there is a certain effect. If another person helps, the result is the sum of their efforts. If two micro-particles are pushing another microparticle, however, the resulting effect may not necessarily be the sum their efforts. A recent study published in Nature Communications, measured this odd effect that scientists call “many body.”

In the microscopic world, where the modern miniaturized machines at the new frontiers of technology operate, as long as we are in the presence of two...

Im Focus: Tiny microbots that can clean up water

Researchers from the Max Planck Institute Stuttgart have developed self-propelled tiny ‘microbots’ that can remove lead or organic pollution from contaminated water.

Working with colleagues in Barcelona and Singapore, Samuel Sánchez’s group used graphene oxide to make their microscale motors, which are able to adsorb lead...

Im Focus: ORNL researchers discover new state of water molecule

Neutron scattering and computational modeling have revealed unique and unexpected behavior of water molecules under extreme confinement that is unmatched by any known gas, liquid or solid states.

In a paper published in Physical Review Letters, researchers at the Department of Energy's Oak Ridge National Laboratory describe a new tunneling state of...

Im Focus: Bionic Lightweight Design researchers of the Alfred Wegener Institute at Hannover Messe 2016

Honeycomb structures as the basic building block for industrial applications presented using holo pyramid

Researchers of the Alfred Wegener Institute (AWI) will introduce their latest developments in the field of bionic lightweight design at Hannover Messe from 25...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

The “AC21 International Forum 2016” is About to Begin

27.04.2016 | Event News

Soft switching combines efficiency and improved electro-magnetic compatibility

15.04.2016 | Event News

Grid-Supportive Buildings Give Boost to Renewable Energy Integration

12.04.2016 | Event News

 
Latest News

Quantum Logical Operations Realized with Single Photons

03.05.2016 | Physics and Astronomy

Discovery of a fundamental limit to the evolution of the genetic code

03.05.2016 | Life Sciences

Cavitation aggressive intensity greatly enhanced using pressure at bubble collapse region

03.05.2016 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>