In this new work, the research team, which included Carnegie's Chang-sheng Zha, Zhenxian Liu, and Russell Hemley, developed new techniques to measure hydrogen samples at pressures above 3 million times normal atmospheric pressure (above 300 GPa) and at temperatures ranging from -438 F (12 K) to close to room temperature..
"These new static compression techniques have opened a window on the behavior of hydrogen at never-before-reached static pressures and temperatures," said Hemley, director of the Geophysical Laboratory.
The team found that the molecular state was stable to remarkably high pressures, confirming extraordinary stability of the chemical bond between the atoms. Their work disproves the interpretations of experiments by other researchers reported last year indicating a metallic state under these conditions. Evidence for semimetallic behavior in the dense molecular phase was found in the new study, but the material must have electrical conductivity well below that of a full metal.