New Structures of gold discovered at extreme pressures

Shane McGlaun - Aug 5, 2019, 7:28 am CDT
New Structures of gold discovered at extreme pressures

Researchers at the Lawrence Livermore National Laboratory (LLNL) and the Carnegie Institution of Washington have announced that a new study they have performed has found a new structure of gold. The team has discovered a new structure for the precious metal when it is compressed very rapidly.

According to the scientists, when gold is compressed over nanoseconds, the increase in pressure and temperature changes the crystalline structure to a new phase of gold. The well-known body-centered cubic (bcc) structure is changed into a more open crystalline structure than the fcc (face-centered cubic) structure. Gold prefers to be in an fcc structure according to the team.

Lead study author Richard Briggs from the LLNL said that the team has discovered a new structure in gold that exists at extreme states. The pressure required to produce the new structure in the gold was two-thirds of the pressure found at the center of the Earth. Briggs also notes that the new structure has less efficient packing at higher pressures than the starting pressure, which was a surprising finding.

The experiments were performed at the Dynamic Compression Sector (DCS) at the Advanced Photon Source, Argonne National Laboratory. The experiments found that the structure of gold began to change at a pressure of 220 GPa, which is 2.2 million times Earth’s atmospheric pressure. Gold started to melt when compressed beyond 250 GPa.

Briggs says that observation of gold at 330 GPa is “astonishing” noting that the experiment measured gold at more than 300 GPa higher than the previous measurement of liquid gold at high pressure. He also noted that many of the theoretical models of gold used to understand high-pressure/high-temperature behavior didn’t predict the formation of bcc structure and that only two out of more than ten published works did.

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