Rewriting Chemical Rules: Researchers Accidentally Create Unprecedented New Gold Compound

SLAC scientists created gold hydride in extreme lab conditions. The work sheds light on dense hydrogen and fusion processes.

By chance and for the first time, an international team of researchers led by scientists at the U.S. Department of Energy’s SLAC National Accelerator Laboratory succeeded in creating solid binary gold hydride—a compound composed solely of gold and hydrogen atoms.

The team had originally set out to investigate how hydrocarbons, molecules made of carbon and hydrogen, transform into diamonds under extreme pressure and heat. During experiments at the European XFEL (X-ray Free-Electron Laser) in Germany, they placed hydrocarbon samples with a thin layer of gold foil, intended only to absorb X-rays and transfer heat to the relatively weakly absorbing hydrocarbons. Unexpectedly, alongside diamond formation, they observed the creation of gold hydride.

“It was unexpected because gold is typically chemically very boring and unreactive – that’s why we use it as an X-ray absorber in these experiments,” explained Mungo Frost, a staff scientist at SLAC and the study’s lead author. “These results suggest there’s potentially a lot of new chemistry to be discovered at extreme conditions where the effects of temperature and pressure start competing with conventional chemistry, and you can form these exotic compounds.”

The findings, published in Angewandte Chemie International Edition, demonstrate how chemical behavior can shift dramatically under extreme environments, such as those found deep inside planets or within hydrogen-fusing stars.

Studying dense hydrogen

To achieve these results, the researchers compressed hydrocarbon samples to pressures exceeding those inside Earth’s mantle using a diamond anvil cell. They then exposed the samples to bursts of X-ray pulses from the European XFEL, heating them above 3,500 degrees Fahrenheit. By analyzing how the X-rays scattered from the samples, the team tracked the structural changes taking place.

As anticipated, the data confirmed that carbon atoms had arranged into a diamond lattice. However, they also revealed unexpected signals: hydrogen atoms had reacted with the gold foil to form gold hydride.

At the conditions generated in the experiment, hydrogen existed in a dense, “superionic” state, in which hydrogen atoms moved freely within the rigid gold lattice. This behavior enhanced the conductivity of the gold hydride, offering new insight into the behavior of materials under extreme pressures and temperatures.

Hydrogen, which is the lightest element of the periodic table, is tricky to study with X-rays because it scatters X-rays only weakly. Here, however, the superionic hydrogen interacted with the much heavier gold atoms, and the team was able to observe hydrogen’s impact on how the gold lattice scattered X-rays. “We can use the gold lattice as a witness for what the hydrogen is doing,” Mungo said.

The gold hydride offers a way to study dense atomic hydrogen under conditions that might also apply to other situations that are experimentally not directly accessible. For example, dense hydrogen makes up the interiors of certain planets, so studying it in the lab could teach us more about those foreign worlds. It could also provide new insights into nuclear fusion processes inside stars like our sun and help develop technology to harness fusion energy here on Earth.

Exploring new chemistry

In addition to paving the way for studies of dense hydrogen, the research also offers an avenue for exploring new chemistry. Gold, which is commonly regarded as an unreactive metal, was found to form a stable hydride at extremely high pressure and temperature. In fact, it appears to be only stable at those extreme conditions as when it cools down, the gold and hydrogen separate. The simulations also showed that more hydrogen could fit in the gold lattice at higher pressure.

The simulation framework could also be extended beyond gold hydride. “It’s important that we can experimentally produce and model these states under these extreme conditions,” said Siegfried Glenzer, High Energy Density Division director and professor for photon science at SLAC and the study’s principal investigator. “These simulation tools could be applied to model other exotic material properties in extreme conditions.”

Reference: “Synthesis of Gold Hydride at High Pressure and High Temperature” by Mungo Frost, Kilian Abraham, Alexander F. Goncharov, R. Stewart McWilliams, Rachel J. Husband, Michal Andrzejewski, Karen Appel, Carsten Baehtz, Armin Bergermann, Danielle Brown, Elena Bykova, Anna Celeste, Eric Edmund, Nicholas J. Hartley, Konstantin Glazyrin, Heinz Graafsma, Nicolas Jaisle, Zuzana Konôpková, Torsten Laurus, Yu Lin, Bernhard Massani, Maximilian Schörner, Maximilian Schulze, Cornelius Strohm, Minxue Tang, Zena Younes, Gerd Steinle-Neumann, Ronald Redmer and Siegfried H. Glenzer, 4 August 2025, Angewandte Chemie International Edition.
DOI: 10.1002/anie.202505811

Parts of this work were supported by the DOE Office of Science.

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