Gold was thought to remain stable forever; however, a new WSU Institute for Shock Physics study found that it changes into a different related crystal structure under enough shock wave pressure. The study, in which scientists tested humankind’s most valuable metals to determine how much pressure they could take, revealed something unexpected about Platinum.
Scientists found that when put under the kind of pressure found at the planet’s core, only Platinum holds up better than gold because it maintains its atomic structure.
Yogendra Gupta, director of the Institute for Shock Physics at WSU, said, “No one expected this. We thought that gold was stable forever, but it turns out it changed into a different related crystal structure under enough shock wave pressure. So basically, if you want a material that will never change, then store Platinum.”
In a series of studies from July 2019–July 2020, scientists subjected four precious metals to increasingly extreme dynamic pressures to determine the most durable ones.
The pressure in the core of the Earth, 3.5 million atmospheres, was tested on all the materials, but only Platinum’s structure remained intact. The metal maintained its shape up to over 4 million atmospheres, at which point it melted after reaching a temperature of 3,215 degrees Fahrenheit.
This was surprising for scientists. In the case of gold, the metal underwent a structural transformation at a relatively modest 1.5 million atmospheres. In the case of silver, it changed at around the same pressure as gold. An experiment with copper revealed that the metal lasted a little longer before transforming at 1.7 million atmospheric pressure.
Gupta said, “It’s just fun science more than anything, but I find it fascinating. I laugh because you will never produce 1.5 million atmospheric pressure in any real-world scenario. For all practical purposes, gold is stable.”
“Other than pure fun science though, the research suggests platinum may make a better pressure and temperature standard than gold for shock physics experiments.”
For this study, scientists used a powerful laser to subject different materials to pressures up to 4 million atmospheres over intervals of about 10–15 billionths of a second. They then used a synchrotron to send x‑ray pulses into the materials to study what happens to their physical structure under immense pressure.
Gupta said, “We can look inside things and provide information about their atomic structure. This is the only synchrotron-based facility in the U.S. capable of doing these kinds of experiments, which have practical applications in various fields such as defense and manufacturing.”