In a twist no one expected, scientists have accidentally forged a rare and exotic compound—gold hydride, a material made entirely of gold and hydrogen atoms, in the fiery crucible of a high-pressure physics experiment.
The breakthrough, led by researchers from the U.S. Department of Energy’s SLAC National Accelerator Laboratory, came while studying diamond formation under extreme conditions at the European XFEL (X-ray Free-Electron Laser) in Germany. But instead of just diamonds, what emerged from the crucible was something scientists didn’t even think possible: a compound involving gold, a metal so chemically inert it’s known for doing absolutely nothing in most reactions.
“We didn’t expect this at all,” said Mungo Frost, a staff scientist at SLAC and lead author of the new study, published in Angewandte Chemie International Edition. “Gold is famously unreactive. That’s why we use it in electronics and as a stable reference in experiments. But here, it reacted—and that changes everything.”
A Curious Experiment Turns Revolutionary
The team’s original goal wasn’t to unlock new chemistry—it was to understand how hydrocarbons (compounds made of hydrogen and carbon) transform into diamonds when squeezed and scorched under conditions mimicking the deep interiors of planets.
To simulate those brutal environments, researchers packed hydrocarbons into diamond anvil cells, devices that squeeze materials with pressures higher than those found in Earth’s mantle. They then blasted the samples with ultrafast, high-intensity X-ray pulses from the European XFEL, heating them to over 3,500 degrees Fahrenheit.
To help absorb the X-rays more efficiently, they placed thin gold foils in the samples. Gold was never meant to participate in the reaction—it was just there to act as a passive heat absorber. But as the X-rays hammered the sample and the heat climbed, something incredible happened.
Diamonds did form from the carbon, as expected. But so did gold hydride, a compound in which hydrogen atoms bind within gold’s crystal lattice, forming a previously unseen solid-state material under these extreme conditions.
Gold Hydride: Chemistry at the Edge of Reality
The formation of gold hydride is more than just a chemical curiosity—it represents a profound shift in how scientists understand chemistry at extreme conditions.
Gold, with its full outer electron shell, is one of the least reactive elements on Earth. But under immense pressure and heat, those usual rules start to break down. Hydrogen, when forced into a dense, “superionic” state, becomes more than just the universe’s lightest element—it becomes electrically conductive and highly mobile, capable of infiltrating even the most closed atomic structures.
In the experiment, hydrogen atoms slipped into gold’s tightly packed structure and moved freely through it, interacting with the gold atoms in ways never before seen. The gold lattice didn’t just tolerate this intrusion—it transformed.
The researchers were able to detect the presence and behavior of hydrogen—ordinarily a challenge in X-ray studies because of its small size—by watching how the heavier gold atoms were affected. As Mungo Frost explained, “We can use the gold lattice as a witness for what the hydrogen is doing.”
This superionic behavior means hydrogen ions flow like a fluid within the solid gold framework, dramatically increasing electrical conductivity. This kind of exotic material could offer a new avenue for exploring how matter behaves in the cores of gas giant planets, where pressures and temperatures dwarf anything found on Earth.
Peering into Alien Worlds and Stellar Interiors
What makes this discovery so thrilling is not just that it happened, but what it might teach us about the universe.
Hydrogen in dense, superionic form is believed to be a key component in the interiors of giant planets like Jupiter and Saturn. These alien environments, under immense gravitational pressure, may host forms of matter that don’t exist anywhere else in the universe—or at least, didn’t until now.
By recreating these conditions in the lab and forming compounds like gold hydride, scientists can begin to study the behaviors of planetary interiors, without needing to send a probe plunging through Jupiter’s crushing atmosphere.
But the implications don’t stop at planets. Hydrogen is also the primary fuel in stars, where it fuses under tremendous pressure to form helium, releasing the energy that powers the Sun and all life on Earth. Understanding how hydrogen behaves under such conditions could inform nuclear fusion research—the quest to create star-like reactions in reactors on Earth to provide nearly limitless, clean energy.
A Glimpse Into the Future of Chemistry
Beyond its planetary and stellar implications, this discovery cracks open a new door in materials science. Gold hydride was stable only under the ultra-high-pressure, high-temperature conditions of the experiment. As the system cooled, the compound separated back into gold and hydrogen.
But this fleeting existence is enough to ignite a major shift in thinking. It suggests that even the most chemically resistant elements can form novel compounds, given the right environment.
Simulations indicate that even more hydrogen can be packed into gold’s lattice under higher pressures. The potential to build super-dense materials with unique electronic or optical properties could inspire new forms of matter, and even materials with applications in next-generation computing, superconductors, or quantum devices.
These discoveries also provide validation for advanced computer simulations that model atomic interactions at extreme conditions. As Siegfried Glenzer, director of SLAC’s High Energy Density Division and principal investigator on the study, explained, “It’s important that we can experimentally produce and model these states under extreme conditions. These simulation tools could be applied to model other exotic material properties.”
In short, gold hydride might be just the beginning.
An Unexpected Discovery That Redefines Possibility
What began as a relatively routine high-pressure experiment became an accidental odyssey into uncharted chemical territory. It’s a powerful reminder of science’s enduring truth: some of the most important discoveries are the ones you didn’t set out to find.
The creation of solid gold hydride isn’t just a fascinating new chapter in the story of matter—it’s a challenge to the very rules that define chemistry. It shows us that under the right conditions, even the noblest of elements can be transformed. It’s proof that there is still magic to be found in the furnace of exploration, where pressure and curiosity collide.
And perhaps most profoundly, it’s a glimpse of how much more there is to discover—beneath our feet, in the hearts of stars, and in the spaces where we never thought to look.
More information: Mungo Frost et al, Synthesis of Gold Hydride at High Pressure and High Temperature, Angewandte Chemie International Edition (2025). DOI: 10.1002/anie.202505811
