Gold’s Hidden Side: How Scientists Accidentally Discovered a New Compound in the Lab

Scientists at SLAC accidentally created solid binary gold hydride while studying diamond formation under extreme conditions, revealing exotic chemistry, planetary insights, and a new way to study dense hydrogen.

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When Gold Met Hydrogen

In science, some of the most exciting breakthroughs happen by accident. That’s exactly what occurred when an international team, led by scientists at the US Department of Energy’s SLAC National Accelerator Laboratory, stumbled upon something no one had made before: solid binary gold hydride — a compound containing nothing but gold and hydrogen atoms. What’s more? It wasn’t even the experiment they’d set out to do.

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Gold is actually edible!

It’s biologically inert, meaning it passes through the body without being absorbed or causing harm, which is why it’s sometimes used to decorate luxury desserts and drinks.

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A Plan for Diamonds, Not Chemistry Shocks

The researchers were originally chasing a different goal entirely: understanding how hydrocarbons — simple compounds made of carbon and hydrogen — transform into diamonds when subjected to extreme heat and crushing pressure.

The European XFEL facility in Germany, with its intense X-ray pulses, was the perfect playground for this work. The setup included hydrocarbon samples alongside a tiny strip of gold foil. The gold’s job was purely practical: absorb X-rays and help heat the hydrocarbons, which are otherwise poor absorbers.

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Then Came the Surprise

“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,” said Mungo Frost, staff scientist at SLAC and lead author of the study. “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.”

Instead of just creating diamonds, the team’s data showed something stranger — gold atoms had bonded with hydrogen atoms to form gold hydride.

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Recreating Planetary Pressure

To simulate conditions deeper than Earth’s mantle, the scientists used a diamond anvil cell to squeeze the samples to unimaginable pressures. Then, they blasted them with X-rays, heating them to more than 3,500°F.

By analysing how the X-rays scattered, the team could watch — in a sense — atoms rearranging themselves. The expected diamond patterns were there, but so were signals that pointed to hydrogen interacting with the gold foil.

Under these extreme conditions, hydrogen entered a “superionic” state — still dense, but with atoms moving freely through the rigid gold structure, making the compound far more conductive than gold alone.

Hydrogen usually resists being “seen” in X-ray experiments, because it barely scatters X-rays. But here, the gold lattice acted like a witness. “We can use the gold lattice as a witness for what the hydrogen is doing,” Frost explained.

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Why This Matters Beyond Earth

The creation of gold hydride isn’t just a quirky lab success — it opens a window into environments we can’t physically reach. Dense hydrogen, like the kind trapped in this compound, exists deep inside planets such as Jupiter and Saturn. Understanding its behaviour could give scientists new clues about planetary interiors, star formation, and even the nuclear fusion processes that power the Sun.

And, of course, any step toward mastering fusion here on Earth could bring humanity closer to a powerful new energy source.

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Gold’s Reputation, Challenged

Gold is famous for being unreactive — the metal that doesn’t tarnish, corrode, or easily bond with other elements. Yet here it was, forming a stable hydride. The stability lasted only under the extreme heat and pressure of the experiment. Once cooled, the gold and hydrogen parted ways.

Computer simulations hinted that even more hydrogen could be forced into the gold structure if the pressure were ramped up further.

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

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The Start of a New Chemistry Playbook

While the initial goal had been to study diamond formation, the real prize turned out to be this unexpected chemistry. Gold hydride may only exist in a narrow window of temperature and pressure, but discovering it proves that the “unreactive” metals of the periodic table might behave very differently under the right conditions.

As Frost summed it up: “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.”

Sometimes, the most valuable discoveries are the ones you never planned to make.