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Physics societies warn of ‘irrecoverable damage’ from European open-access plan

The European Physical Society (EPS) has warned that a major open-access initiative in Europe could cause “irrecoverable damage” if it is implemented too quickly. In a statement, the EPS says that while it welcomes the proposal – known as Plan S — as a “medium to long-term vision”, its proponents must get more support by engaging further with the scientific community.

Plan S is an ambitious attempt to make research papers open access immediately after they are published. It was unveiled in September 2018 by 11 national research funding organizations — dubbed cOAlition S – that include UK Research and Innovation and the French National Research Agency. The group says that all scientific publications resulting from research funded by public grants provided by “national and European research councils and funding bodies” must be published in “compliant” open-access journals or on open-access platforms from 1 January 2020.

If implemented, the agreement means that authors funded by these agencies would not be allowed to publish in so-called “hybrid” journals, with funders being able to sanction researchers who are not compliant with the rules. Hybrid journals are publications that remain subscription based but give authors the choice to make their papers open access for a fee, known as an article-processing charge.

Reaching a tipping point

While the EPS states that it supports open science and that the physics community has often pioneered its implementation, it argues that several governing principles for Plan S are not “conducive” to a transition to open access. Notably, the EPS says that a forced transition in such a short period of time could “undermine the economic viability of many journals”, which would cause “irrecoverable damage to established, well-functioning networks of editors and referees”. The society adds that publication in open-access repositories can only “complement, not replace” publication in peer-reviewed outlets.

The EPS also warns that non-European authors may not have access to the same level of open-access funding as in Europe and that such a plan can “only succeed” when it is coordinated globally. A solely Euro-centric implementation, the society says, risks “accentuat[ing] knowledge divides, both inside Europe and between north and south”. In addition, the EPS is concerned that Plan S limits researchers’ freedom to choose where to publish, which could be a problem as academic recruitment and career advancement are still based on publication metrics and journal prestige.

Some of the EPS’s views are also shared by the Institute of Physics (IOP), which publishes Physics World. In a statement released today, the IOP calls on cOAlition S to extend the timeline for transition to fully open access and to continue to support the hybrid model until a “natural tipping point” has been reached. “As more funders and countries support open access, so a larger proportion of articles in IOPP’s journals will be published on an open access basis and they will be in a position to convert,” the IOP says. The statement also underlines the importance of income from publishing for learned societies, such as the IOP.

Springer Nature – the largest publisher of open-access papers – also says cOAlition S should rethink its opposition to hybrid journals. In a statement released earlier this week, it advises the group to carry out research to demonstrate the benefits of open access so that more funders and scientists support it. The company also calls for “highly selective journals and those with significant levels of non-primary research content need” to be treated differently.

The statements from the publishers follow an open letter published in November 2018 by over 1700 scientists that called Plan S a “serious violation of academic freedom”. They noted that while Plan S was written with good intentions, the ban on hybrid journals would cause a “big problem” and that the initiative also threatens to split the global scientific community into two separate systems.

Satellites barely evade collision, stars are born in Van Gogh’s work, and scientists experiment with limoncello

A couple of weeks ago the small satellite company Capella was alerted that another craft was on a high-speed collision course with their pathfinder, Denali. Manoeuvre commands were urgently sent to the satellite and the crisis was averted, although the two objects still passed each other very closely.

Space may be great and vast but it’s getting crowded closer to Earth. According to the European Space Agency (ESA), more than 29,000 large pieces of debris are orbiting our planet – and many more smaller bits besides. And as smaller satellites, such as the one that flew past Denali, often don’t have propulsion systems to help them avoid impact, the risk of these numbers growing is increasing.

You can find out more about orbital debris on the ESA website.

Many have gazed upon Vincent van Gogh’s The Starry Night in wonder. But if you’re a scientist, those famous spirals – all of varying sizes – in the painted sky might remind you instead of turbulent flow. After all, Andrei Kolmogorov’s 1941 description of subsonic turbulence does rely on vortices of different length scales.

Researchers in Australia have now published a paper weighing in on whether van Gogh’s famous artwork does indeed depict realistic turbulence.

After calculating a 2D power spectrum on a square region of painted sky, they concluded that the sky of The Starry Night is actually far more reminiscent of the supersonic turbulent flow inside molecular gas clouds. Such conditions are known to be the birthplace of stars in the universe, a coincidence that’s oddly fitting.

Now, as it’s the weekend, you might be looking forward to a cheeky glass of limoncello, the liqueur originating from southern Italy. But did you know that while water-repellent industrial chemicals usually require surfactants to mix with water, in limoncello the alcohol effortlessly keeps the citrus oil and water together.

Scientists from the Institut Laue Langevin have now examined the microscopic composition of the liqueur. They uncovered that limoncello is composed of tiny oil droplets in a water-alcohol mix. And if we can work out how the mixture forms, it could lead to many applications for essential oils in specialty chemicals as well as environmentally friendly plastics and insect repellents.

You can find out more about the research in ACS Omega.

Non-contact technique measures vital signs in conscious small animals

Measuring the vital signs of small conscious animals is important for assessing their health and behaviour. Current monitoring techniques, such as electrocardiograms (ECG), ultrasound and auscultation (listening to heart and breath sounds), however, rely on close skin contact with the animal and other invasive approaches. Such methods can cause discomfort or stress to animals and may even require anaesthesia, particularly for birds, reptiles and fish.

To address this problem, Xiaonan Hui and Edwin Kan from Cornell University are developing a less invasive way to monitor the health of small animals, based on radio-frequency (RF) near-field coherent sensing (NCS). They note that this approach has minimal impact on the daily rhythms of the animal, with most unlikely to even notice the ongoing measurements (Science Advances 10.1126/sciadv.aau0169).

Hui and Kan investigated two NCS setups. The first involves a wireless system that uses a harmonic RF identification (RFID) architecture with inexpensive passive sensing tags. In this setup, a harmonic reader transmits the downlink signal at a frequency, f, through the reader transmit antenna. This signal powers up a passive harmonic RFID tag placed in the vicinity of the animal and is converted to a second-harmonic frequency at 2f (the NCS sensing signal).

As long as the animal is within the near-field range of the sensing tag antenna, motion on and inside its body is coupled to the backscattered signal and sent to the harmonic reader’s receive antenna. This approach, deployable without need of maintenance, is suitable for use in the animals’ natural habitats with weather-proof RFID tags and the reader placed nearby.

The second approach replaces the wireless links between the reader and the harmonic tag with RF cables. Here, the harmonic reader transmits the NCS sensing signal directly at 2f and is placed in the near-field range of the animal under test. The NCS signal modulated by the animal’s vital signs is received by the reader antenna. This design reduces interference and is appropriate for deployment in an indoor laboratory.

To compare their NCS approach to current monitoring methods, Hui and Kan first performed synchronized NCS and ECG measurements on an anesthetized rat. The heartbeat intervals extracted from NCS and ECG data matched very closely. The researchers suggest that NCS is sufficiently accurate to replace ECG for behaviour studies based on heart rate variation.

Next, they demonstrated the possibility of using non-invasive NCS on several species of small conscious animals, in which monitoring methods such as ECG are difficult, if not impossible. These included a pet golden hamster, a parakeet, a Russian tortoise and a betta fish.

Hamster under measurement
Hamster under measurement with the sensing tag. (Courtesy: Xiaonan Hui, Cornell University)

The hamster, for example, was monitored in its cage using both wireless and wired NCS applied from outside the cage. The researchers acquired respiratory and heartbeat waveforms without the hamster being aware of the device. The heartbeat waveform features were similar for each beat during the recording, and were similar to those in the anesthetized rat (with 20% longer heartbeat intervals).

The researchers also successfully detected detailed features of heartbeat and respiration in the parakeet and tortoise. A heartbeat was thought to have been recorded in the fish, but further studies are needed to confirm this finding.

“Our NCS system with convenient setup not only provides the previously unachievable sensing capability but also improves the animal testing protocols with no harm to their welfare or interference to their circadian rhythms,” Hui and Kan conclude. “Our demonstrations can be further adapted to other species and laboratory settings to provide more humane study, care and assessment of animals; our method also provides measurement of unbiased vital signs of animals monitored in their natural state.”

LIGO upgrade to allow ‘almost daily’ detection of gravitational waves

The UK and US have announced a $35m upgrade to the Advanced Laser Interferometer Gravitational-wave Observatory (aLIGO). The improvement will see the twin observatories — located near Hanford, Washington and Livingston, Louisiana in the US – double their sensitivity to gravitational waves. Work on the upgrade will start in 2023 and be complete two years later.

Each LIGO facility works by sending twin laser beams down two 4 km-long tubes – arranged as an L-shape – that are kept under a near-perfect vacuum. The beams are reflected back down the tubes by mirrors precisely positioned at the ends of each arm.  As a gravitational wave passes through the observatory, it causes extremely tiny distortions in the distance travelled by each laser beam.

LIGO first turned on 2002 and was upgraded between 2010 and 2015 to improve the facilities’ ability to spot gravitational waves by a factor of 10. Thanks to this $221m upgrade – known as Advanced LIGO, or aLIGO – researchers can detect gravitational waves that originate anywhere within a sphere of about 420 million light-years in radius, centred on the Earth.

That breakthrough was announced in February 2016 when researchers working on aLIGO directly detected gravitational waves for the first time in an event in September 2015 – when aLIGO was being calibrated. The waves were produced from the collision of two black holes of 36 and 29 solar masses, respectively, which merged to form a spinning, 62-solar-mass black hole, some 1.3 billion light-years (410 mpc) away in an event dubbed GW150914. The finding ended the decades-long hunt for these ripples in space–time and marked the beginning of a new era of gravitational-wave astronomy that has since resulted in around 10 gravitational-wave events being detected including from the merger of two neutron stars.

Reducing noise

While aLIGO is set to begin another operating run in the next couple of months, plans are now afoot to boost its sensitivity even further. The US National Science Foundation (NSF) announced today that it will provide $20.4m for a further upgrade to the facility, dubbed aLIGO+. The UK Research and Innovation, meanwhile, will provide a further $14.1m with additional support from the Australian Research Council.

The upgrades will include applying new coatings to the mirrors to reduce thermal noise as well as improvements to the laser system. aLIGO+’s capabilities are expected to probe the origins and evolution of stellar-mass black holes as well as allow precision tests of extreme gravity and enable detailed study of the equation of state of neutron stars.

“This award ensures that LIGO will continue to lead in gravitational wave science for the next decade,” says NSF Director France Córdova. “These detections may reveal secrets from inside supernovae and teach us about extreme physics from the first seconds after the universe’s birth.”

According to David Reitze, executive director of the LIGO Laboratory, the upgrades will see the observatory being able to detect binary black hole collisions on “an almost daily basis”. The improvement will also be made “as standard” to the planned LIGO facility in India, which, if built, is expected to come online in 2025.

Diamond spins come into focus using new measurement technique

A new method to read out the spin states of individual negatively-charged nitrogen vacancy (NV–) centres has been developed by researchers in Europe and Japan. The technique could make today’s bulky read-out systems obsolete and enable new uses of NV– centres in electronic devices. It could also be used to read-out NV- centres that are very close together, which could be useful for developing quantum-information technologies.

A nitrogen vacancy occurs when two adjacent carbon atoms in a diamond lattice are replaced by a nitrogen atom and an empty lattice site. Together, the nitrogen atom and the vacancy can behave as a negatively-charged entity with an intrinsic spin. NV– centres are isolated from their surroundings, which means that their quantum behaviour is not immediately washed out by thermal fluctuations. As a result, they can be used to create a range of quantum technologies that operate at room temperature.

A green photon hitting an NV– centre can promote an electron to an excited state. As it decays back to the ground state, it may emit a red photon. The NV– centre has three spin sublevels, whose excited states have different probabilities of emitting a photon when they decay. By exciting an individual NV– centre repeatedly and collecting the red photons emitted, therefore, researchers can detect its spin state – which is extremely useful for quantum computation. Moreover, because the spin state can be influenced by external variables such as magnetic field, electric field, temperature, force and pressure, NV– centres can therefore been used as atomic-scale sensors.

Bulky detection

Although NV– centres are tiny, the equipment required to collect the red photons is bulky and complicated. This has prevented the integration of NV– centres into chip-sized devices. It also poses a problem for using NV– centres in room-temperature quantum computing. Entangling two NV– centres requires them to be about 30 nm apart, which is much smaller than the diffraction limit for red light. As a result, detecting the spin states separately requires difficult and expensive microscopy techniques.

Also, the finite lifetime of the excited state slows down experiments: “To get information about the NV centre’s spin state, you have to repeat the measurement many times,” explains Milos Nesladek of Hasselt University in Belgium: “You can put in only a certain amount of laser power before the optical signature saturates.”

Nesladek and colleagues have created an alternative method of detecting an NV- centre’s spin that also uses green laser light. However, the same physics that causes the excited states of NV– centres with different spins to have different fluorescence on decay also causes them to have different probabilities of absorbing a second photon from the same laser. This removes the extra electron from the NV– centre into the conduction band of the diamond. If a voltage is applied, the electron can move freely through the diamond and be detected. Measuring the photocurrent produced when light hits a specific NV– centre therefore allows researchers to infer its spin state. This process was first unveiled by Nesladek and colleagues in 2015 for NV– centre ensembles. The new work extends this to detection of single NV– centre spins.

Stronger signal

The researchers demonstrated a higher signal-to-noise ratio than possible with optical detection under the same conditions. Furthermore, they found that, as the photocurrent was produced when electrons were promoted from the excited state rather than when they decayed from it, it continued to increase when they turned up the laser power. Most importantly, says team member Petr Siyushev of the University of Ulm in Germany, “you don’t need to implement complicated optical detection: you can just integrate everything into a tiny diamond chip which will be compatible with all current electronic technology”.

Ronald Walsworth of Harvard University in the US describes the work as “a very important technical step.” He cautions that the optics required to target specific NV– centres with green light are still quite complex, and says electrical readout presents its own difficulties: “You need to fabricate electrodes in specific places on the diamond,” he says. “Once you do that you can’t easily image many NVs over a wide field of view.” Nevertheless, he believes the technique has real promise for applications such as use of NV centres in cryogenics: “Getting good optical detection of red photons coming all the way out of a cryostat is a real challenge,” he says, “With electrical detection that would become very straightforward.”

The research is described in Science.

Superinsulating aerogel resists mechanical and thermal shocks

A new mechanically strong, double-pane ceramic aerogel made from hexagonal boron nitride that is resistant to high temperatures could be used in aerospace and industrial applications. The material, which boasts both a negative Poisson’s ratio and a negative thermal expansion coefficient, is very different to typical ceramic aerogels that are brittle and structurally degrade under thermal shocks.

Aerogels are exceptionally lightweight, composite materials containing more than 99% air. They can withstand high temperatures and are resistant to many chemicals. Most aerogels studied so far, however, are made from ceramic materials, such as silica, alumina and silicon carbide, and are thus very brittle.

Researchers recently made aerogels from graphene (a sheet of carbon just one atom thick). Here, the nanosheets of carbon stack up against each other, which makes the material incredibly strong. The nanosheets also divide the aerogel into nanosized cells through which air cannot pass. This means that the material has a thermal conductivity that is lower than that of air.

Sacrificial template

A team led by Xiangfeng Duan of the University of California, Los Angeles, has made a structurally similar aerogel from another 2D material, hexagonal boron nitride (hBN) by using a porous graphene aerogel as a sacrificial template. The researchers grew their aerogel using modified hydrothermal reduction and non-contact freeze-drying techniques. They used borazine as the hBN precursor and then grew hBN layers on top of the graphene structure using chemical vapour deposition.

Since hBN resists oxidation better than graphene and has a higher thermal stability as well, they are easily able to remove the graphene using a thermal etching process to leave behind the pure hBN aerogel.

The resulting material has a density as low as 0.1 mg/cm3 thanks to its highly porous structure with atomically thin cell walls (made of highly crystalline hBN), is superelastic (it can be compressed to 5% of its original length without breaking and fully recovers), and has an ultralow thermal conductivity (of around 2.4 mW/m∙K in vacuum and 20 mW/m∙K in air). It can also withstand sharp temperature shocks in that it can be heated to 900°C and then rapidly cooled to -198°C at a rate of 275°C per second over several hundred cycles while hardly losing any of its strength.

Careful microstructure engineering

The material’s superior properties come from the fact that it has both a negative Poisson’s ratio (it contracts inwards when compressed) and a negative thermal expansion coefficient (it contracts when heated). Duan and colleagues were able to confer both these properties (which are the opposite to conventional materials) onto their aerogel by carefully engineering its microstructure through hierarchical structuring and produce a material with hyperbolic frameworks. These have saddle shapes with negative curvature.

“The sub-cell wall features in our aerogel also have a double-pane architecture that reduces wall thickness without compromising the mechanical strength of the material and facilitates out-of-plane vibration modes for the negative thermal expansion coefficient effect,” Duan tells Physics World. “Such walls also retard heat transfer by gas molecules to ensure very low thermal conductivity.”

According to the researchers, the new ceramic aerogels could be used as thermal insulation in applications that require extreme temperatures, such as spacecraft and automobile components. Since the material also has a high surface area of more than 1080 m2/g, a value that is higher than those reported for other ultra-light materials (around 800 m2/g for silica or carbon aerogels), it might also be used in applications that call for high surface-to-volume ratios, like gas catalysis and thermal energy storage.

The team, reporting its work in Science, says that it is now busy making ceramic aerogels with even better flexibility and robustness, higher working temperatures and lower thermal conductivity.

Food webs alter as warmer seas change colour

The Blue Planet is to get a little bluer as the world warms and climates change. Where the seas turn green, expect an even deeper verdant tint, new research suggests.

Since humans began increasing the levels of greenhouse gases in the atmosphere – by burning the fossil fuels that have provided the energy for both economic growth and a population explosion – the oceans have warmed in ways that affect marine life. They have grown ever more acidic, in ways that affect coral growth and fish behaviour.

But when US and British scientists tested a model of ocean physics, biogeochemistry and ecosystems – intending to simulate changes in the populations of marine phytoplankton or algae – they also incorporated some of the ocean’s optical properties. Since green plants photosynthesize, they absorb sunlight, and change reflectivity.

And, as mariners have known for centuries, the blue ocean is blue because levels of marine life in the warmer mid-ocean waters are very low.

The researchers tweaked their simulation to see what the world would look like in 2100 if humanity carried on burning fossil fuels on the notorious business-as-usual scenario and took global average temperatures up to 3°C above historic levels.

And they found that higher temperatures would alter the global palette. More than half of the world’s oceans would intensify in colour. The subtropics would become even more blue, and the oceans that sweep around the poles would become an even deeper green, they report in the journal Nature Communications.

“The models suggest the changes won’t appear huge to the naked eye, and the ocean will still look like it has blue regions in the subtropics and greener regions near the equator and the poles,” says Stephanie Dutkiewicz, of the Massachusetts Institute of Technology, who led the research

Wider effects

“That basic pattern will still be there. But it will be enough different that it will affect the rest of the food web that phytoplankton supports.”

The clearer the water, the bluer the reflection of the sunlight. From space, the world looks blue. Waters rich in phytoplankton are by definition rich too in chlorophyll that absorbs blue wavelengths and reflects a green tint. But changes in chlorophyll colouring, observed over the decades from satellite monitoring, can be affected by natural climate cycles and shifts in nutrient supply.

The researchers were looking for a more complete model of the wavelengths of visible light that are absorbed, scattered or reflected by living things. They devised one, and tested their new model against satellite evidence so far. When they found agreement with the past, they had also found yet another way to read the future

Explaining ecosystem change

They tuned their simulated planet to the 3 °C warming that seems inevitable unless humans rapidly shift from fossil fuels to renewable energy sources, to discover that wavelengths of light around the blue-green spectrum shifted the fastest. The shifts in colour could tell a story of altered ecosystems.

“The nice thing about this model is that we can use it as a laboratory, a place where we can experiment, to see how our planet is going to change,” Dutkiewicz says.

“There will be a noticeable difference in the colour of 50% of the ocean by the end of the 21st century. It could be potentially quite serious.

“Different types of phytoplankton absorb light differently, and if climate change shifts one community of phytoplankton to another, they will also change the types of food webs they can support.”

Photonics innovations, carbon continues to amaze, and diversity in the 2D materials community

In this episode of Physics World Weekly, we start by discussing some of the latest developments in light-based technologies. Susan Curtis discusses her recent trip to San Francisco where she attended a double-header of conferences – BIOS and Photonics West. Hear about photonics technologies in medicine and the hardware being developed Facebook to handle ever-increasing volumes of data.

Later in the podcast, Anna Demming reports about her recent trip to Tokyo where she attended Nano Tech 2019. She found out why carbon continues to amaze materials scientists with its useful properties and versatility. Anna also catches up with ICREA Research Professor Stephan Roche, the editor-in-chief of the journal JPhys Materials, which is produced by IOP Publishing (the parent company of Physics World). The journal is currently putting together a special issue where all lead authors of papers are women.

As always, we also bring you a roundup of some of the most interesting research stories making the headlines this week on our website.

If you enjoy what you hear, you can subscribe to Physics World Weekly via the Apple podcast app or your chosen podcast host.

Avoid large groups to be a disruptive scientist

Smaller teams of scientists tend to carry out work that is more “disruptive” than that of larger groups, according to a study of more than 65 million papers, patents and software products published between 1954 and 2014. The study, led by James Evans from the University of Chicago, finds that as teams grow from one to 50 members there is a big drop in scientific “disruptiveness”. Large groups instead mostly carry out work that develops on existing research.

To assess whether work can be classed as disruptive, the researchers looked at the citations of their 65 million research outputs. In particular, they examined whether the work cites the references of another paper’s references. Work that cites many references in another paper it cites is considered to be building on and consolidating previous research, while work that refers to few of its reference’s citations is classed as disruptive.

The researchers found that solo authors are 72% more likely to be highly disruptive – in other words in the top 5% of disruptive papers – than teams of five. Teams of 10, meanwhile, are 50% more likely to have a higher impact papers than smaller teams, but these papers were unlikely to be highly disruptive. When validating their work, the researchers found that Nobel-prize-winning papers are among the 2% most disruptive papers, while review articles are among the least disruptive. They also asked academics to propose articles that they thought were disruptive and developed on existing ideas, which again aligned with their analysis.

‘Collaboration fetish’

Evans told Physics World that he thinks smaller teams have more to gain and less to lose from disruption as they cannot compete with larger teams when it comes to building on previous work. This pushes them to explore possibilities that “don’t gel with but could disrupt” current scientific and technological trends. Evans says that clashes in large teams also reduce the number of ideas and steer members towards things they have in common.

Evans adds that the findings and the growth of large teams should concern anyone interested in the long-term viability of science. “Scientific funding agencies and technology financing needs to undertake more risks associated with the higher likelihood of failure and disruptive success that characterise small team research,” he says.

The disruption measure used by the researchers was based on work carried out by Jason Owen-Smith, a sociologist at the University of Michigan, who told Physics World that the findings have practical implications for how society funds and supports science. “It suggests that in an era of ‘big science’ it is also important to identify and support work by smaller teams across diverse settings,” he says, adding that it also signals the importance of research that “may not be directed at any particular near-term goal for the overall progress of science”.

That view is backed up by Pierre Azoulay from the Massachusetts Institute of Technology, who told Physics World that the time is right to end the “collaboration fetish”. “Enough with funding mechanisms that predicate funding on collaboration of this kind or that kind,” says Azoula, who was not involved in the study. “There is nothing wrong with collaboration, but there is no reason for policy makers and funders to think that they can engineer collaboration in ways that are necessarily going to be wonderful.”

Computational methods lead researchers to more precise chemistry

As our global energy demand increases, the need for sustainable routes to sources of energy and industrial chemicals becomes more urgent. Catalysis – the process by which a chemical increases the rate of a reaction – is the key to unlocking such routes. Research has therefore focused on development of new catalytic materials like photocatalysts, nanocatalysts, and electrocatalysts.

But what, exactly, makes a chemical compound a good catalyst?

Scott Denmark’s group at the University of Illinois hopes to answer that question using computer science. In their new paper in Science (DOI: 10.1126/science.aau5631), the group shows the power of information science in chemistry – a field called chemoinformatics – in predicting a compound’s catalytic activity.

“Experimental catalysis design allows researchers to qualitatively recognize patterns in catalyst structures to improve catalyst selectivity and efficiency,” says Andrew Zahrt, first-author of the paper and PhD student in chemistry. “This is an empirical method that does not always have or lead to mechanistic understanding of chemical reactions.”

Having this mechanistic understanding is key for catalysis, as a subtle change in a molecule’s structure – corresponding to an energy difference of about 1 kcal/mol between structures – can lead to large, measurable changes in catalyst performance. The ability to predict these changes can alleviate the burden of having to synthesize and test hundreds of molecules to optimize a given chemical system.

A new workflow for chemists

Their code first produces an in silico library that provides a collection of synthetically available catalysts for a particular system. Their code then calculates chemical descriptors for the catalysts and uses the results of those calculations to determine a subset of catalysts – called a “universal training set” – to examine experimentally. Zahrt describes the process:

“We calculate a conformer distribution and put it in a common grid comparable across all catalysts. The numbers themselves that we use are occupancy grid points in each point of space,” he said.  “It’s like taking an image map, and taking an average occupancy to capture their flexibility – we want to answer the question: how much time does this group spend near an active site?”

The system eliminates the need for any prior mechanistic information about the system, as the system examines the structure of the catalysts to understand their properties. The group has been able to experimentally verify their findings and is now working on looking at larger material libraries. Currently, Zahrt says their progress is limited by the calculation of the initial conformer distribution; the code takes about one month to run for their library of 800 materials.

“We’re comparing very similar molecules. All we’re doing is changing subunits, but this can have dramatic changes,” Zahrt says. “This is definitely a model system, this is definitely a proof of concept stage.”

More details can be found in Science.

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