Science
Identifying a new, cleaner source for white light – Phys.org
When early humans discovered how to harness fire, they were able to push back against the nightly darkness that enveloped them. With the invention and widespread adoption of electricity, it became easier to separate heat from light, work through the night, and illuminate train cars to highways. In recent years, old forms of electric light generation such as halogen lightbulbs have given way to more energy efficient alternatives, further cheapening the costs to brighten our homes, workplaces, and lives generally.
Unfortunately, however, white light generation by newer technologies such as light-emitting diodes (LEDs) is not straightforward and often relies on a category of materials called “rare-earth metals,” which are increasingly scarce. This has recently led scientists to look for ways to produce white light more sustainably. Researchers at Giessen University, the University of Marburg, and Karlsruhe Institute of Technology have recently uncovered a new class of material called a “cluster glass” that shows great potential for replacing LEDs in many applications.
“We are witnessing the birth of white-light generation technology that can replace current light sources. It brings all the requirements that our society asks for: availability of resources, sustainability, biocompatibility,” said Prof. Dr. Simone Sanna, Giessen University Professor and lead computational researcher on the project.
“My colleagues from the experimental sciences, who observed this unexpected white light generation, asked for theoretical support. Cluster glass has an incredible optical response, but we don’t understand why. Computational methods can help to understand those mechanisms. This is exactly the challenge that theoreticians want to face.”
Sanna and his collaborators have turned to the power of high-performance computing (HPC), using the Hawk supercomputer at the High-Performance Computing Center Stuttgart (HLRS) to better understand cluster glass and how it might serve as a next-generation light source. They published their findings in Advanced Materials.
Clear-eyed view on cluster glass formation
If you are not a materials scientist or chemist, the word glass might just mean the clear, solid material in your windows or on your dinner table. Glass is actually a class of materials that are considered “amorphous solids;” that is, they lack an ordered crystalline lattice, often due to a rapid cooling process. At the atomic level, their constituent particles are in a suspended, disordered state. Unlike crystal materials, where particles are orderly and symmetrical across a long molecular distance, glasses’ disorder at the molecular level make them great for bending, fragmenting, or reflecting light.
Experimentalists from the University of Marburg recently synthesized a particular of glass called a “cluster glass.” Unlike a traditional glass that almost behaves as a liquid frozen in place, cluster glass, as the name implies, is a collection of separate clusters of molecules that behave as a powder at room temperature. They generate bright, clear, white light upon irradiation by infrared radiation. While powders cannot easily be used to manufacture small, sensitive electronic components, the researchers found a way to re-cast them in glass form: “When we melt the powder, we obtain a material that has all the characteristics of a glass and can be put in any form needed for a specific application,” Sanna said.
While experimentalists were able to synthesize the material and observe its luminous properties, the group turned to Sanna and HPC to better understand how cluster glass behaves the way it does. Sanna pointed out that white light generation isn’t a property of a single molecule in a system, but the collective behaviors of a group of molecules. Charting these molecules’ interactions with one another and with their environment in a simulation therefore means that researchers must both capture the large-scale behaviors of light generation and also observe how small-scale atomic interactions influence the system. Any of these factors would be computationally challenging. Modeling these processes at multiple scales, however, is only possible using leading HPC resources like Hawk.
Collaboration between experimentalists and theoreticians has become increasingly important in materials science, as synthesizing many iterations of a similar material can be slow and expensive. High-performance computing, Sanna indicated, makes it much faster to identify and test materials with novel optical properties. “The relationship between theory and experiment is a continuous loop. We can predict the optical properties of a material that was synthesized by our chemist colleagues, and use these calculations to verify and better understand the material’s properties,” Sanna said. “We can also design new materials on a computer, providing information that chemists can use to focus on synthesizing compounds that have the highest likelihood of being useful. In this way, our models inspire the synthetization of new compounds with tailored optical properties”
In the case of cluster glass, this approach resulted in an experiment that was verified by simulation, with modeling helping to show the researchers the link between the observed optical properties and the molecular structure of their cluster glass material and can now move forward as a candidate to replace light sources heavily reliant on rare-earth metals.
HPC expedites R&D timelines
HPC plays a major role in helping researchers accelerate the timeline between new discovery and new product or technology. Sanna explained that HPC drastically cut down on the time to get a better understanding of cluster glass. “We spend a lot of time doing simulation, but it is much less than characterizing these materials in reality,” he said. “The clusters we model have a diamond-shaped core with 4 ligands (molecular chains) attached to it. Those ligands can be made of any number of things, so doing this in an experiment is time consuming.”
Sanna pointed out that the team is still limited by how long they can perform individual runs for their simulations. Many research projects on supercomputers can divide a complex system into many small parts and run calculations for each part in parallel. Sanna’s team needs to pay special attention to long-distance particle interactions across large systems, so they are limited by how much they can divide their simulation across computer nodes. He indicated that having regular access to longer run times—more than a day straight on a supercomputer—would allow the team to work more quickly.
In ongoing studies of cluster glass Sanna’s team hopes to thoroughly understand the origin of its light generating properties. This could help to identify additional new materials and to determine how best to apply cluster glass in light generation.
Sanna explained that HPC resources at HLRS were essential for his team’s basic science research, which he hopes will lead to new products that can benefit society. “The main computational achievement in this journal article was only possible through our access to the machine in Stuttgart,” he said.
Explore further
Irán Rojas‐León et al, Cluster‐Glass for Low‐Cost White‐Light Emission, Advanced Materials (2022). DOI: 10.1002/adma.202203351
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High-Performance Computing Center Stuttgart
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Identifying a new, cleaner source for white light (2022, August 16)
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SpaceX sent up the 30th launch from the Space Coast for the year on the evening of April 23, a mission that also featured the company’s 300th successful booster recovery.
A Falcon 9 rocket carrying 23 of SpaceX’s Starlink internet satellites blasted off at 6:17 p.m. Eastern time from Cape Canaveral Space Force Station’s Space Launch Complex 40.
The first-stage booster set a milestone of the 300th time a Falcon 9 or Falcon Heavy booster made a successful recovery landing, and the 270th time SpaceX has reflown a booster.
This particular booster made its ninth trip to space, a resume that includes one human spaceflight, Crew-6. It made its latest recovery landing downrange on the droneship Just Read the Instructions in the Atlantic Ocean.
The company’s first successful booster recovery came in December 2015, and it has not had a failed booster landing since February 2021.
The current record holder for flights flew 11 days ago making its 20th trip off the launch pad.
SpaceX has been responsible for all but two of the launches this year from either Kennedy Space Center or Cape Canaveral with United Launch Alliance having launched the other two.
SpaceX could knock out more launches before the end of the month, putting the Space Coast on pace to hit more than 90 by the end of the year, but the rate of launches by SpaceX is also set to pick up for the remainder of the year with some turnaround times at the Cape’s SLC-40 coming in less than three days.
That could amp up frequency so the Space Coast could surpass 100 launches before the end of the year, with the majority coming from SpaceX. It hosted 72 launches in 2023.
More launches from ULA are on tap as well, though, including the May 6 launch atop an Atlas V rocket of the Boeing CST-100 Starliner with a pair of NASA astronauts to the International Space Station.
ULA is also preparing for the second launch ever of its new Vulcan Centaur rocket, which recently received its second Blue Origin BE-4 engine and is just waiting on the payload, Sierra Space’s Dream Chaser spacecraft, to make its way to the Space Coast.
Blue Origin has its own rocket it wants to launch this year as well, with New Glenn making its debut as early as September, according to SLD 45’s range manifest.
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SpaceX launch marks 300th successful booster landing (2024, April 24)
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The common loon, that icon of northern wilderness, is under threat from climate change due to declining water clarity. Published earlier this month in the journal Ecology, a study conducted by biologists from Chapman University and Rensselaer Polytechnic Institute in the U.S. has demonstrated the first clear evidence of an effect of climate change on this species whose distinct call is so tied to the soundscape of Canada’s lakes and wetlands.
Through the course of their research, the scientists found that July rainfall results in reduced July water clarify in loon territories in Northern Wisconsin. In turn, this makes it difficult for adult loons to find and capture their prey — mainly small fish — underwater, meaning they are unable to meet their chicks’ metabolic needs. Undernourished, the chicks face higher mortality rates. The consistent foraging techniques used by loons across their range means this impact is likely echoed wherever they are found — from Alaska to Canada to Iceland.
The researchers used Landsat imagery to find that there has been a 25-year consistent decline in water clarity, and during this period, body weights of adult loon and chicks alike have also declined. With July being the month of most rapid growth in young loons, the study also pinpointed water clarity in July as being the greatest predictor of loon body weight.
One explanation for why heavier rainfall leads to reduced water clarity is the rain might carry dissolved organic matter into lakes from adjacent streams and shoreline areas. Lawn fertilizers, pet waste and septic system leaks may also be to blame.
The researchers, led by Chapman University professor Walter Piper, hope to use these insights to further conservation efforts for this bird Piper describes as both “so beloved and so poorly understood.”
Return of the king
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The artwork and publicity materials showcasing a giant salmon that lived five million years ago were ready to go to promote a new exhibit, when the discovery of two fossilized skulls immediately changed what researchers knew about the fish.
Initial fossil discoveries of the 2.7-metre-long salmon in Oregon in the 1970s were incomplete and had led researchers to mistakenly suggest the fish had fang-like teeth.
It was dubbed the “sabre-toothed salmon” and became a kind of mascot for the Museum of Natural and Cultural History at the University of Oregon, says researcher Edward Davis.
But then came discovery of two skulls in 2014.
Davis, a member of the team that found the skulls, says it wasn’t until they got back to the lab that he realized the significance of the discovery that has led to the renaming of the fish in a new, peer-reviewed study.
“There were these two skulls staring at me with sideways teeth,” says Davis, an associate professor in the department of earth sciences at the university.
In that position, the tusk-like teeth could not have been used for biting, he says.
“That was definitely a surprising moment,” says Davis, who serves as director of the Condon Fossil Collection at the university’s Museum of Natural and Cultural History.
“I realized that all of the artwork and all of the publicity materials and bumper stickers and buttons and T-shirts we had just made two months prior, for the new exhibit, were all out of date,” he says with a laugh.
Davis is co-author of the new study in the journal PLOS One, which renames the giant fish the “spike-toothed salmon.”
It says the salmon used the tusk-like spikes for building nests to spawn, and as defence mechanisms against predators and other salmon.
The salmon lived about five million years ago at a time when Earth was transitioning from warmer to relatively cooler conditions, Davis says.
It’s hard to know exactly why the relatives of today’s sockeye went extinct, but Davis says the cooler conditions would have affected the productivity of the Pacific Ocean and the amount of rain feeding rivers that served as their spawning areas.
Another co-author, Brian Sidlauskas, says a fish the size of the spike-toothed salmon must have been targeted by predators such as killer whales or sharks.
“I like to think … it’s almost like a sledgehammer, these salmon swinging their head back and forth in order to fend off things that might want to feast on them,” he says.
Sidlauskas says analysis by the lead author of the paper, Kerin Claeson, found both male and female salmon had the “multi-functional” spike-tooth feature.
“That’s part of our reason for hypothesizing that this tooth is multi-functional … It could easily be for digging out nests,” he says.
“Think about how big the (nest) would have to be for an animal of this size, and then carving it out in what’s probably pretty shallow water; and so having an extra digging tool attached to your head could be really useful.”
Sidlauskas says the giant salmon help researchers understand the boundaries of what’s possible with the evolution of salmon, but they also capture the human imagination and a sense of wonder about what’s possible on Earth.
“I think it helps us value a little more what we do still have, or I hope that it does. That animal is no longer with us, but it is a product of the same biosphere that sustains us.”
This report by The Canadian Press was first published April 24, 2024.
Brenna Owen, The Canadian Press
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