Unlike systems such as graphene on copper, where atoms may diffuse into the substrate without forming a distinct alloy, the boron atoms in this case formed a defined 2D copper boride — a new compoundwith a distinct atomic structure. The finding, published in Science Advances by researchers from Rice and Northwestern University, sets the stage for further exploration of a relatively untapped class of 2D materials.

“Borophene is still a material at the brink of existence, and that makes any new fact about it important by pushing the envelope of our knowledge in materials, physics and electronics,” said Yakobson, Rice’s Karl F. Hasselmann Professor of Engineering and professor of materials science and nanoengineering and chemistry. “Our very first theoretical analysis warned that on copper, boron would bond too strongly. Now, more than a decade later, it turns out we were right — and the result is not borophene, but something else entirely.”

Previous studies successfully synthesized borophene on metals like silver and gold, but copper remained an open — and contested — case. Some experiments suggested boron might form polymorphic borophene on copper, while others suggested it could phase-separate into borides or even nucleate into bulk crystals. Resolving these possibilities required a uniquely detailed investigation combining high-resolution imaging, spectroscopy and theoretical modeling.

“What my experimentalist colleagues first saw were these rich patterns of atomic resolution images and spectroscopy signatures, which required a lot of hard work of interpretation,” Yakobson said.

These efforts revealed a periodic zigzag superstructure and distinct electronic signatures, both of which deviated significantly from known borophene phases. A strong match between experimental data and theoretical simulations helped resolve a debate about the nature of the material that forms at the interface between the copper substrate and the near-vacuum environment of the growth chamber.

Although copper boride was not the material researchers set out to make, its discovery offers important insight into how boron interacts with different metal substrates in two-dimensional environments. The work expands the knowledge on the formation of atomically thin metal boride materials — an area that could inform future studies of related compounds, including those with known technological relevance, such as metal borides among ultra-high temperature ceramics, which are of great interest for extreme environments and hypersonic systems.

“2D copper boride is likely to be just one of many 2D metal borides that can be experimentally realized. We look forward to exploring this new family of 2D materials that have broad potential use in applications ranging from electrochemical energy storage to quantum information technology,” said Mark Hersam , Walter P. Murphy Professor of Materials Science and Engineering at Northwestern University, who is a co-corresponding author on the study.

The discovery comes shortly after another boron-related breakthrough by the same Rice theory team. In a separate study published in ACS Nano , researchers showed that borophene can form high-quality lateral, edge-to-edge junctions with graphene and other 2D materials, offering better electrical contact than even “bulky” gold. The juxtaposition of the two findings highlights both the promise and the challenge of working with boron at the atomic scale: its versatility allows for surprising structures but also makes it difficult to control.

“Those images we initially saw in the experimental data looked quite mysterious,” Yakobson said. “But in the end, it all fell into place and provided a logical answer — metal boride, bingo! This was unexpected at first, but now, it is settled — and the science can move forward.”

The research was supported by the Office of Naval Research (N00014-21-1-2679), the National Science Foundation (DMR-2308691) and the United States Department of Energy (2801SC0012547). The content herein is solely the responsibility of the authors and does not necessarily represent the official views of the funding organizations and institutions.

First, the interface of both enzyme and molecule should be located at their respective smaller end. This way, a strong coupling between both of them can be achieved. For the same reason, the conformational change in the enzyme should not be smaller than in the reaction. Finally, the conformational change of the enzyme has to take place fast enough to maximize the chemical driving force of the reaction.

“We built our research on two main pillars,” Ramin Golestanian, director of MPI-DS describes the approach. “Conservation of momentum and coupling between the reaction coordinates,” he continues. Thus, the researchers expanded the view of a classical 2-dimensional reaction coordinate. Typically, models for enzymatic reactions define an energy barrier that has to be overcome in order for the reaction to take place.

“As in our model we also consider the enzyme dynamics and coupling, we go beyond this existing concept, considering two reaction coordinates,” say Michalis Chatzittofi, first author of the study. “Instead of overcoming an energy barrier, one can now imagine alternative ways to bypass it by taking alternative routes,” he concludes.

These results provide a new basis for the design of molecular machines, avoiding the tedious and technically challenging approach to simulate the dynamics of each atom individually.

Now, MIT scientists may have solved the mystery. They propose that a combination of an ancient, weak magnetic field and a large, plasma-generating impact may have temporarily created a strong magnetic field, concentrated on the far side of the moon.

In a study appearing in the journal Science Advances, the researchers show through detailed simulations that an impact, such as from a large asteroid, could have generated a cloud of ionized particles that briefly enveloped the moon. This plasma would have streamed around the moon and concentrated at the opposite location from the initial impact. There, the plasma would have interacted with and momentarily amplified the moon’s weak magnetic field. Any rocks in the region could have recorded signs of the heightened magnetism before the field quickly died away.

This combination of events could explain the presence of highly magnetic rocks detected in a region near the south pole, on the moon’s far side. As it happens, one of the largest impact basins — the Imbrium basin — is located in the exact opposite spot on the near side of the moon. The researchers suspect that whatever made that impact likely released the cloud of plasma that kicked off the scenario in their simulations.

“There are large parts of lunar magnetism that are still unexplained,” says lead author Isaac Narrett, a graduate student in the MIT Department of Earth, Atmospheric and Planetary Sciences (EAPS). “But the majority of the strong magnetic fields that are measured by orbiting spacecraft can be explained by this process — especially on the far side of the moon.”

Narrett’s co-authors include Rona Oran and Benjamin Weiss at MIT, along with Katarina Miljkovic at Curtin University, Yuxi Chen and Gábor Tóth at the University of Michigan at Ann Arbor, and Elias Mansbach PhD ’24 at Cambridge University. Nuno Loureiro, professor of nuclear science and engineering at MIT, also contributed insights and advice.

Beyond the sun

Scientists have known for decades that the moon holds remnants of a strong magnetic field. Samples from the surface of the moon, returned by astronauts on NASA’s Apollo missions of the 1960s and 70s, as well as global measurements of the moon taken remotely by orbiting spacecraft, show signs of remnant magnetism in surface rocks, especially on the far side of the moon.

The typical explanation for surface magnetism is a global magnetic field, generated by an internal “dynamo,” or a core of molten, churning material. The Earth today generates a magnetic field through a dynamo process, and it’s thought that the moon once may have done the same, though its much smaller core would have produced a much weaker magnetic field that may not explain the highly magnetized rocks observed, particularly on the moon’s far side.

An alternative hypothesis that scientists have tested from time to time involves a giant impact that generated plasma, which in turn amplified any weak magnetic field. In 2020, Oran and Weiss tested this hypothesis with simulations of a giant impact on the moon, in combination with the solar-generated magnetic field, which is weak as it stretches out to the Earth and moon.

In simulations, they tested whether an impact to the moon could amplify such a solar field, enough to explain the highly magnetic measurements of surface rocks. It turned out that it wasn’t, and their results seemed to rule out plasma-induced impacts as playing a role in the moon’s missing magnetism.

A spike and a jitter

But in their new study, the researchers took a different tack. Instead of accounting for the sun’s magnetic field, they assumed that the moon once hosted a dynamo that produced a magnetic field of its own, albeit a weak one. Given the size of its core, they estimated that such a field would have been about 1 microtesla, or 50 times weaker than the Earth’s field today.

From this starting point, the researchers simulated a large impact to the moon’s surface, similar to what would have created the Imbrium basin, on the moon’s near side. Using impact simulations from Katarina Miljkovic, the team then simulated the cloud of plasma that such an impact would have generated as the force of the impact vaporized the surface material. They adapted a second code, developed by collaborators at the University of Michigan, to simulate how the resulting plasma would flow and interact with the moon’s weak magnetic field.

These simulations showed that as a plasma cloud arose from the impact, some of it would have expanded into space, while the rest would stream around the moon and concentrate on the opposite side. There, the plasma would have compressed and briefly amplified the moon’s weak magnetic field. This entire process, from the moment the magnetic field was amplified to the time that it decays back to baseline, would have been incredibly fast — somewhere around 40 minutes, Narrett says.

Would this brief window have been enough for surrounding rocks to record the momentary magnetic spike? The researchers say, yes, with some help from another, impact-related effect.

They found that an Imbrium-scale impact would have sent a pressure wave through the moon, similar to a seismic shock. These waves would have converged to the other side, where the shock would have “jittered” the surrounding rocks, briefly unsettling the rocks’ electrons — the subatomic particles that naturally orient their spins to any external magnetic field. The researchers suspect the rocks were shocked just as the impact’s plasma amplified the moon’s magnetic field. As the rocks’ electrons settled back, they assumed a new orientation, in line with the momentary high magnetic field.

“It’s as if you throw a 52-card deck in the air, in a magnetic field, and each card has a compass needle,” Weiss says. “When the cards settle back to the ground, they do so in a new orientation. That’s essentially the magnetization process.”

The researchers say this combination of a dynamo plus a large impact, coupled with the impact’s shockwave, is enough to explain the moon’s highly magnetized surface rocks — particularly on the far side. One way to know for sure is to directly sample the rocks for signs of shock, and high magnetism. This could be a possibility, as the rocks lie on the far side, near the lunar south pole, where missions such as NASA’s Artemis program plan to explore.

“For several decades, there’s been sort of a conundrum over the moon’s magnetism — is it from impacts or is it from a dynamo?” Oran says. “And here we’re saying, it’s a little bit of both. And it’s a testable hypothesis, which is nice.”

The team’s simulations were carried out using the MIT SuperCloud. This research was supported, in part, by NASA.