'Cracking the Glass Problem': ASU physics alumna part of national collaboration
Most often when we think of glass, we think of the panes in our windows and the dishes on our tables. And most of us feel we have a basic grasp on the concept of glass as a material — the sand melts, and then artists somehow blow and mold it into the things we use, both practical and decorative.
However, at a molecular level, glass is actually quite mysterious. Physicists are seeking to understand exactly how and why it does what it does — transitioning from a solid to a liquid and then back to a solid with an entirely new use and appearance.
Arizona State University physics doctoral alumna Varda Faghir Hagh is one of the physicists collaborating on a national level to learn as much as they can about glass and its behavior.
Hagh completed her PhD at ASU in June 2018. Her thesis research was in the rigidity of disordered materials — namely glass. She studied how their structures can be mapped into networks, and how they change when acted upon by pressures or forces.
By the time she officially graduated that December, she was already working in her current appointment — as a postdoctoral researcher at the University of Chicago in Illinois and a collaborator on the Simons Collaboration "Cracking the Glass Problem" project.
Hagh also has a courtesy appointment at the University of Oregon and has traveled to work in several other locations, including Santa Barbara, California, and Syracuse, New York.
“Because I’m collaborating, I’m a rotating postdoc, so my job also gives me the opportunity to travel a lot, which I love,” she said.
Disordered and marginally stable
Building on her doctoral research, Hagh is now studying the nature of marginally stable materials — especially how they react and change when compressed or jammed into a state that can be easily changed by even a small amount of force or deformation.
The word “disordered,” applied to material like glass, refers to its molecular structure. Crystals, for example, are very orderly in their structure — their atoms and molecules are placed in a very neat and predictable pattern, so that representative data on how they respond can be easily used to predict and understand other crystal properties and scenarios.
When early physicists began classifying materials, they initially hypothesized that all solid materials had orderly, crystal structures.
However, they soon discovered many solid materials that fell outside of that pattern, with atoms and molecules placed in a far less predictable fashion.
The nature of disordered structure makes understanding and predicting the nature of these materials far more complicated. It also makes for more complicated structures and materials that can be changed and manipulated with comparative ease. Because of this, most of the materials we currently surround ourselves with are classified as “disordered.”
By careful study of the properties of disordered, glassy structures in their jammed transition state, Hagh can compare her findings to existing theories of what they might do, which will tell us more about the behavior of glasses in general.
The other scientists in Simons Collaboration are examining different aspects of glassy structures and their properties, a project they are calling “Cracking the Glass Problem.” A better understanding of these structures, and how they behave and respond, would mean new methods in developing smarter materials. While we are familiar with obvious uses of glass in buildings, dishes, and decor, from a material physics perspective it actually encompasses a far wider range and is used in countless things we encounter on a daily basis. Foams, pastes, coffee grounds, flour and most granular structures, and of course in our technologies like smartphone and computer screens.
Hagh’s particular focus of the jamming transition has many possible applications in food processing and transportation — maintaining existing structures under heat and pressure and building new ones. Perhaps if we understand why the jamming transition happens, we can understand how to stop it from happening.
When she is not studying glassy structures on a molecular level, Hagh enjoys a related activity — glass blowing and sculpting.
Alongside her physics research at ASU, Hagh took sculpting classes that she felt contributed to her studies and helped her develop the skills to bring her creative ideas into 3D reality.
“I really enjoy working with my hands,” Hagh said. “Sometimes sitting at a computer all day and working with abstract ideas, you want to do something physical and realize something tangible.”
The gift of physics
Hagh found her love of physics while in high school in her home country of Iran.
“I was just generally interested in understanding how things worked in the world,” she said. “I was amazed by learning how machines worked, or looking up at the night sky and wondering about the universe, and how it was operating.”
She obtained her undergraduate and master's degrees in physics at the University of Tehran in Iran, and then decided to come to the United States to pursue a PhD.
“Physics has taught me a lot of great things,” she said, citing both a general knowledge of the universe and also the essential ability to be a critical thinker. “When you get a degree in physics it helps you get a job in a large number of areas and gives you the ability to do a lot of things that you might not be able to do with other degrees."
Her initial vision of what it would mean to be a physics scholar was a little different than the reality.
“I had read popular science books and I thought you just sat in a room and dreamed up theories,” she said. “But, what I learned, and what I wish people knew, is that physics is not just making up theories and ideas — even though it might sometimes sound very abstract.
“Science is a very particular and accurate way of gathering data and collecting information, and then testing them over and over, again and again, to make sure that’s reflecting the truth of the nature and not just reflecting what one person thinks is right or correct. I think that’s the biggest gift that physics has given me. I have this passion for learning, and physics has always encouraged me to learn more and more about the world, and I really value it personally.”
This solid foundation, combined with the many opportunities available to her through ASU, prepared Hagh for the work she is currently taking on.
“I worked with Michael Thorpe, who does really seminal work in glasses,” she said. “The center for biological physics — there are a lot of good people who are doing really high-quality computational work, and interacting and being around them on a daily basis helped me have all the skills they were looking for when they posted this position."
Hagh also took advantage of opportunities to participate in research programs off campus. Encouraged by her advisors, she applied to two summer schools, where she met and worked with others studying in her area, including several she is working with now.
“Also, my adviser would encourage me to go to conferences and present my work,” Hagh said. Two of her published papers that grew from contacts gained during these conference experiences were very collaborative and tied in nicely with the work she would be doing on the Simons Collaboration.
“The collaborative nature of my work and the fact that my adviser encouraged me to do this is how I got this position,” she said of her posting at the University of Chicago.
Ultimately, Hagh hopes to remain in academia and become faculty somewhere to play her part in contributing to the next generation.
However, anything that will let her tackle an interesting problem is always on the docket, and she will certainly continue her research. The possibilities of being involved in new and exciting research areas, and working with groups such as the Allen Institute for Brain Science, or Google Brain, hold a definite fascination.
“Even though I have not done specific research in this area, I have picked up a lot of skills that hold a lot of crossover through my collaborations,” she said. “ But of course we will see how things go.”