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Department of Physics

The Cavendish Laboratory
 

AI tackles the challenge of materials structure prediction

Wed, 27/07/2022 - 18:46

The researchers, from Cambridge and Linkoping Universities, have designed a way to predict the structure of materials given its constitutive elements. The results are reported in the journal Science Advances.

The arrangement of atoms in a material determines its properties. The ability to predict this arrangement computationally for different combinations of elements, without having to make the material in the lab, would enable researchers to quickly design and improve materials. This paves the way for advances such as better batteries and photovoltaics.

However, there are many ways that atoms can ‘pack’ into a material: some packings are stable, others are not. Determining the stability of a packing is computationally intensive, and calculating every possible arrangement of atoms to find the best one is not practical. This is a significant bottleneck in materials science.

“This materials structure prediction challenge is similar to the protein folding problem in biology,” said Dr Alpha Lee from Cambridge’s Cavendish Laboratory, who co-led the research. “There are many possible structures that a material can ‘fold’ into. Except the materials science problem is perhaps even more challenging than biology because it considers a much broader set of elements.”

Lee and his colleagues developed a method based on machine learning that successfully tackles this challenge. They developed a new way to describe materials, using the mathematics of symmetry to reduce the infinite ways that atoms can pack into materials into a finite set of possibilities. They then used machine learning to predict the ideal packing of atoms, given the elements and their relative composition in the material.

Their method accurately predicts the structure of materials that hold promise for piezoelectric and energy harvesting applications, with over five times the efficiency of current methods. Their method can also find thousands of new and stable materials that have never been made before, in a way that is computationally efficient.  

“The number of materials that are possible is four to five orders of magnitude larger than the total number of materials that we have made since antiquity,” said co-first author Dr Rhys Goodall, also from the Cavendish Laboratory. “Our approach provides an efficient computational approach that can ‘mine’ new stable materials that have never been made before. These hypothetical materials can then be computationally screened for their functional properties.”

The researchers are now using their machine learning platform to find new functional materials such as dielectric materials. They are also integrating other aspects of experimental constraints into their materials discovery approach.

The research was supported in part by the Royal Society and the Winton Programme for the Physics of Sustainability.

Reference:
Rhys A. Goodall et al. ‘Rapid discovery of stable materials by coordinate-free coarse graining.’ Science Advances (2022). DOI: 10.1126/sciadv.abn4117

Researchers have designed a machine learning method that can predict the structure of new materials with five times the efficiency of the current standard, removing a key roadblock in developing advanced materials for applications such as energy storage and photovoltaics.

Our approach provides an efficient computational approach that can ‘mine’ new stable materials that have never been made before. Rhys GoodallMR.Cole_Photographer via Getty ImagesGeometric abstract background with connected line and dots


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Professor Suchitra Sebastian to receive the Schmidt Science Polymaths Award

Thu, 30/06/2022 - 12:30

Professor Suchitra Sebastian from Cambridge’s Cavendish Laboratory has been awarded the Schmidt Science Polymaths award. Schmidt Futures, a philanthropic initiative founded by Eric and Wendy Schmidt, announced ten new recipients of the award, which provides $500,000 a year, paid through their institution, for up to five years to help support part of a research group.

The Polymath programme makes long-term bets on recently-tenured professors with remarkable track records, promising futures, and a desire to explore risky new research ideas across disciplines. The awardees are the second group to receive the Polymath award, joining just two other exceptionally talented interdisciplinary researchers named in 2021. The awards build upon Schmidt Futures’ commitment to identifying and supporting extraordinary talent, and growing networks empowered to solve hard problems in science and society.

Professor Sebastian’s research seeks to discover exotic quantum phases of matter in complex materials. Her group’s experiments involve tuning the co-operative behaviour of electrons within these materials by subjecting them to extreme conditions including low temperature, high applied pressure, and intense magnetic field.

Under these conditions, her group can take materials that are quite close to behaving like a superconductor – perfect, lossless conductors of electricity – and ‘nudge’ them, transforming their behaviour.

“I like to call it quantum alchemy – like turning soot into gold,” Sebastian said. “You can start with a material that doesn’t even conduct electricity, squeeze it under pressure, and discover that it transforms into a superconductor. Going forward, we may also discover new quantum phases of matter that we haven’t even imagined.”

Other awards she has received for her research include the World Economic Forum Young Scientist award, the L'Oreal-UNESCO Fellowship, the Lee Osheroff Richardson North American Science prize, the International Young Scientist Medal in Magnetism, the Moseley Medal, the Philip Leverhulme Prize, the Brian Pippard Prize. She is an ERC starting and consolidator grant awardee. Most recently, she was awarded the New Horizons in Physics Prize (2022) by the Breakthrough Foundation.

In addition to her physics research, Sebastian is also involved in theatre and the arts. She is Director of the Cavendish Arts-Science Project, which she founded in 2016. The programme has been conceived to question and explore material and immaterial universes through a dialogue between the arts and sciences.

“The very idea of the Polymath Award is revolutionary,” said Sebastian. “It's so rare that an award selects people for being polymaths. Imagining new worlds and questioning traditional ways of knowing - whether by doing experimental theatre, or by bringing together art and science, is part of who I am.

“And this is why in our group, we love to research at the edge - to make risky boundary crossings and go on wild adventures into the quantum unknown. We do it because it's incredibly fun, you never know what each day will bring. To be recognised for this by Schmidt Futures is so unexpected and exciting, the possibilities this award opens up are endless. I look forward to embarking on new quantum explorations, it’s going to be a wild ride!”

The awards build upon Schmidt Futures’ commitment to identifying and supporting extraordinary talent, and growing networks empowered to solve hard problems in science and society. Each Polymath will receive support at the moment in their careers when researchers have the most freedom to explore new ideas, use emerging technologies to test risky theories, and pursue novel scientific research that traverses fields and disciplines; which is otherwise unlikely to receive funding or support.

“The interdisciplinary work that could herald the next great scientific breakthroughs are chronically under-funded,” said Eric Braverman, CEO of Schmidt Futures. “We are betting on the talent of the Schmidt Science Polymaths to explore new ideas across disciplines and accelerate discoveries to address the challenges facing our planet and society.”

Hopeful Polymaths from over 25 universities submitted applications outlining research ideas in STEM fields that represent a substantive shift from their current research portfolio and are unlikely to receive funding elsewhere for consideration to the Schmidt Science Polymaths program. Existing Polymaths’ ideas range from the artificial creation of complex soft matter like human tissue, to the development of synthetic biology platforms for engineering multicellular systems, to the discovery of exotic forms of quantum matter. The impact of this type of interdisciplinary research could result in innovations previously thought impossible like a 3D printer for human organs, climate change-resistant crops, or the unknown applications of quantum matter.

“Single-minded -specialisation coupled with rigid research and funding structures often hinder the ambition to unleash fresh perspectives in scientific inquiry,” said Stuart Feldman, Chief Scientist of Schmidt Futures. “From climate change to public health, the Schmidt Science Polymaths utilise the depth of their knowledge across a breadth of fields to find new ways to solve some of our hardest problems for public benefit.”

Cambridge physicist Professor Suchitra Sebastian to join group of ten recently tenured professors named to Polymath Program, awarded up to $2.5 million each for interdisciplinary research support.

To be recognised for this by Schmidt Futures is so unexpected and exciting, the possibilities this award opens up are endless. I look forward to embarking on new quantum explorations, it’s going to be a wild ride!Suchitra SebastianNick SaffellSuchitra Sebastian


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No signs (yet) of life on Venus

Tue, 14/06/2022 - 16:00

Researchers from the University of Cambridge used a combination of biochemistry and atmospheric chemistry to test the ‘life in the clouds’ hypothesis, which astronomers have speculated about for decades, and found that life cannot explain the composition of the Venusian atmosphere.

Any life form in sufficient abundance is expected to leave chemical fingerprints on a planet’s atmosphere as it consumes food and expels waste. However, the Cambridge researchers found no evidence of these fingerprints on Venus.

Even if Venus is devoid of life, the researchers say their results, reported in the journal Nature Communications, could be useful for studying the atmospheres of similar planets throughout the galaxy, and the eventual detection of life outside our Solar System.

“We’ve spent the past two years trying to explain the weird sulphur chemistry we see in the clouds of Venus,” said co-author Dr Paul Rimmer from Cambridge’s Department of Earth Sciences. “Life is pretty good at weird chemistry, so we’ve been studying whether there’s a way to make life a potential explanation for what we see.”

The researchers used a combination of atmospheric and biochemical models to study the chemical reactions that are expected to occur, given the known sources of chemical energy in Venus’s atmosphere.

“We looked at the sulphur-based ‘food’ available in the Venusian atmosphere – it’s not anything you or I would want to eat, but it is the main available energy source,” said Sean Jordan from Cambridge’s Institute of Astronomy, the paper’s first author. “If that food is being consumed by life, we should see evidence of that through specific chemicals being lost and gained in the atmosphere.”

The models looked at a particular feature of the Venusian atmosphere – the abundance of sulphur dioxide (SO2). On Earth, most SO2 in the atmosphere comes from volcanic emissions. On Venus, there are high levels of SO2 lower in the clouds, but it somehow gets ‘sucked out’ of the atmosphere at higher altitudes.

“If life is present, it must be affecting the atmospheric chemistry,” said co-author Dr Oliver Shorttle from Cambridge’s Department of Earth Sciences and Institute of Astronomy. “Could life be the reason that SO2 levels on Venus get reduced so much?”

The models, developed by Jordan, include a list of metabolic reactions that the life forms would carry out in order to get their ‘food’, and the waste by-products. The researchers ran the model to see if the reduction in SO2 levels could be explained by these metabolic reactions.

They found that the metabolic reactions can result in a drop in SO2 levels, but only by producing other molecules in very large amounts that aren’t seen. The results set a hard limit on how much life could exist on Venus without blowing apart our understanding of how chemical reactions work in planetary atmospheres.

“If life was responsible for the SO2 levels we see on Venus, it would also break everything we know about Venus’s atmospheric chemistry,” said Jordan. “We wanted life to be a potential explanation, but when we ran the models, it isn’t a viable solution. But if life isn’t responsible for what we see on Venus, it’s still a problem to be solved – there’s lots of strange chemistry to follow up on.”

Although there’s no evidence of sulphur-eating life hiding in the clouds of Venus, the researchers say their method of analysing atmospheric signatures will be valuable when JWST, the successor to the Hubble Telescope, begins returning images of other planetary systems later this year. Some of the sulphur molecules in the current study are easy to see with JWST, so learning more about the chemical behaviour of our next-door neighbour could help scientists figure out similar planets across the galaxy.

“To understand why some planets are alive, we need to understand why other planets are dead,” said Shorttle. “If life somehow managed to sneak into the Venusian clouds, it would totally change how we search for chemical signs of life on other planets.”

“Even if ‘our’ Venus is dead, it’s possible that Venus-like planets in other systems could host life,” said Rimmer, who is also affiliated with Cambridge’s Cavendish Laboratory. “We can take what we’ve learned here and apply it to exoplanetary systems – this is just the beginning.”

The research was funded by the Simons Foundation and the Science and Technology Facilities Council (STFC), part of UK Research and Innovation (UKRI).

 

Reference:
Sean Jordan, Oliver Shorttle and Paul B. Rimmer. ‘Proposed energy-metabolisms cannot explain the atmospheric chemistry of Venus.’ Nature Communications (2022). DOI: 10.1038/s41467-022-30804-8

The unusual behaviour of sulphur in Venus’ atmosphere cannot be explained by an ‘aerial’ form of extra-terrestrial life, according to a new study.

Even if ‘our’ Venus is dead, it’s possible that Venus-like planets in other systems could host lifePaul RimmerNASA/JPL-CaltechVenus from Mariner 10


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YesLicense type: Public Domain

‘Fruitcake’ structure observed in organic polymers

Thu, 02/06/2022 - 09:35

The field of organic electronics has benefited from the discovery of new semiconducting polymers with molecular backbones that are resilient to twists and bends, meaning they can transport charge even if they are flexed into different shapes.

It had been assumed that these materials resemble a plate of spaghetti at the molecular scale, without any long-range order. However, an international team of researchers found that for at least one such material, there are tiny pockets of order within. These ordered pockets, just a few ten-billionths of a metre across, are stiffer than the rest of the material, giving it a ‘fruitcake’ structure with harder and softer regions.

The work was led by the University of Cambridge and Park Systems UK Limited, with KTH Stockholm in Sweden, the Universities of Namur and Mons in Belgium, and Wake Forest University in the USA. Their results, reported in the journal Nature Communications, could be used in the development of next-generation microelectronic and bioelectronic devices.

Studying and understanding the mechanical properties of these materials at the nanoscale – a field known as nanomechanics – could help scientists fine-tune those properties and make the materials suitable for a wider range of applications.

“We know that the fabric of nature on the nanoscale isn’t uniform, but finding uniformity and order where we didn’t expect to see it was a surprise,” said Dr Deepak Venkateshvaran from Cambridge’s Cavendish Laboratory, who led the research.

The researchers used an imaging technique called higher eigen mode imaging to take nanoscale pictures of the regions of order within a semiconducting polymer called indacenodithiophene-co-benzothiadiazole (C16-IDTBT). These pictures showed clearly how individual polymer chains line up next to each other in some regions of the polymer film. These regions of order are between 10 and 20 nanometres across.

“The sensitivity of these detection methods allowed us to map out the self-organisation of polymers down to the individual molecular strands,” said co-author Dr Leszek Spalek, also from the Cavendish Laboratory. “Higher eigen mode imaging is a valuable method for characterising nanomechanical properties of materials, given the relatively easy sample preparation that is required.”

Further measurements of the stiffness of the material on the nanoscale showed that the areas where the polymers self-organised into ordered regions were harder, while the disordered regions of the material were softer. The experiments were performed in ambient conditions as opposed to an ultra-high vacuum, which had been a requirement in earlier studies.

“Organic polymers are normally studied for their applications in large area, centimetre scale, flexible electronics,” said Venkateshvaran. “Nanomechanics can augment these studies by developing an understanding of their mechanical properties at ultra-small scales with unprecedented resolutions.

“Together, the fundamental knowledge gained from both types of studies could inspire a new generation of soft microelectronic and bioelectronic devices. These futuristic devices will combine the benefits of centimetre scale flexibility, micrometre scale homogeneity, and nanometre scale electrically controlled mechanical motion of polymer chains with superior biocompatibility.”

The research was funded in part by the Royal Society.

 

Reference:
Illia Dobryden et al. ‘Dynamic self-stabilization in the electronic and nanomechanical properties of an organic polymer semiconductor.’ Nature Communications (2022). DOI: 10.1038/s41467-022-30801-x

 

Inset image: Organic polymer film. One region shows the parallel alignment of individual polymer chains confirming nanoscopic order. Such organisation is not visible within the disordered region.

Researchers have analysed the properties of an organic polymer with potential applications in flexible electronics and uncovered variations in hardness at the nanoscale, the first time such a fine structure has been observed in this type of material.  

Deepak VenkateshvaranStructure of C16-IDTBT, an organic polymer


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Existing infrastructure will be unable to support demand for high-speed internet

Tue, 26/04/2022 - 16:00

The researchers, from the University of Cambridge and BT, have established the maximum speed at which data can be transmitted through existing copper cables. This limit would allow for faster internet compared to the speeds currently achievable using standard infrastructure, however it will not be able to support high-speed internet in the longer term.

The team found that the ‘twisted pair’ copper cables that reach every house and business in the UK are physically limited in their ability to support higher frequencies, which in turn support higher data rates.

While full-fibre internet is currently available to around one in four households, it is expected to take at least two decades before it reaches every home in the UK. In the meantime, however, existing infrastructure can be improved to temporarily support high-speed internet.

The results, reported in the journal Nature Communications, both establish a physical limit on the UK’s ubiquitous copper cables, and emphasise the importance of immediate investment in future technologies.

The Cambridge-led team used a combination of computer modelling and experiments to determine whether it was possible to get higher speeds out of existing copper infrastructure and found that it can carry a maximum frequency of about 5 GHz, above the currently used spectrum, which is lower than 1 GHz. Above 5 GHz however, the copper cables start to behave like antennas.

Using this extra bandwidth can push data rates on the copper cables above several Gigabits per second on short ranges, while fibre cables can carry hundreds of Terabits per second or more.

“Any investment in existing copper infrastructure would only be an interim solution,” said co-author Dr Anas Al Rawi from Cambridge’s Cavendish Laboratory. “Our findings show that eventual migration to optical fibre is inevitable.”

The twisted pair– where two conductors are twisted together to improve immunity against noise and to reduce electromagnetic radiation and interference – was invented by Alexander Graham Bell in 1881. Twisted pair cables replaced grounded lines by the end of the 19th century and have been highly reliable ever since. Today, twisted pair cables are standardised to carry 424 MHz bandwidth over shorter cable lengths owing to deeper fibre penetration and advancement in digital signal processing.

These cables are now reaching the end of their life as they cannot compete with the speed of fibre-optic cables, but it’s not possible to get rid of all the copper cables due to fibre’s high cost. The fibre network is continuously getting closer to users, but the connection between the fibre network and houses will continue to rely on the existing copper infrastructure. Therefore, it is vital to invest in technologies that can support the fibre networks on the last mile to make the best use of them.

“High-speed internet is a necessity of 21st century life,” said first author Dr Ergin Dinc, who carried out the research while he was based at Cambridge’s Cavendish Laboratory. “Internet service providers have been switching existing copper wires to high-speed fibre-optic cables, but it will take between 15 and 20 years for these to reach every house in the UK and will cost billions of pounds. While this change is happening, we’ve shown that existing copper infrastructure can support higher speeds as an intermediate solution.”

The Cambridge researchers, working with industry collaborators, have been investigating whether it’s possible to squeeze faster internet speeds out of existing infrastructure as a potential stopgap measure, particularly for rural and remote areas.

“No one had really looked into the physical limitations driving the maximum internet speed for twisted pair cables before,” said Dinc. “If we used these cables in a different way, would it be possible to get them to carry data at higher speeds?”

Using a mix of theoretical modelling and experimentation, the researchers found that twisted pair cables are limited in the frequency they can carry, a limit that’s defined by the geometry of the cable. Above this limit, around 5 GHz, the twisted pair cables start to radiate and behave like an antenna.

“The way that the cables are twisted together defines how high a frequency they can carry,” said Dr Eloy de Lera Acedo, also from the Cavendish, who led the research. “To enable higher data rates, we’d need the cables to carry a higher frequency, but this can’t happen indefinitely because of physical limitations. We can improve speeds a little bit, but not nearly enough to be future-proof.”

The researchers say their results underline just how important it is that government and industry work together to build the UK’s future digital infrastructure, since existing infrastructure can handle higher data rates in the near future, while the move to a future-proof full-fibre network continues.

The work is part of an ongoing collaboration between the Cavendish, the Department of Engineering, BT and Huawei in a project led by Professor Mike Payne, also of the Cavendish Laboratory. The research was also supported by the Royal Society, and the Science and Technology Facilities Council, part of UK Research and Innovation.

 

Reference:
Ergin Dinc et al. ‘High-Frequency Electromagnetic Waves on Unshielded Twisted Pairs: Upper Bound on Carrier Frequency.’ Nature Communications (2022). DOI: 10.1038/s41467-022-29631-8

Researchers have shown that the UK’s existing copper network cables can support faster internet speeds, but only to a limit. They say additional investment is urgently needed if the government is serious about its commitment to making high-speed internet available to all.

We can improve speeds a little bit, but not nearly enough to be future-proofEloy de Lera AcedoJohn Rensten/Getty ImagesMillennium Bridge, London


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