NRC “Kurchatov Institute”, 123182 Moscow, Russia Moscow Institute of Physics and Technology, 141700 Dolgoprudnyi, Russia
Received January 12, 2017, revised February 20, 2017
The molecular phase of hydrogen converts to the atomic metallic phase at high pressures estimated usually as 300–500 GPa. We analyze the zero-temperature decay of metallic phase as the pressure is relieved below the transition one. The metallic state is expected to be in the metastable long-lived state down to about 10–20 GPa and decays instantly at the lower pressures. The pressure range of the long-lived metastable state is directly associated with an impossibility to produce a stable hydrogen molecule immersed into the electron liquid of high density. For lower pressures, the nucleation of an electron-free cavity with the energetically favorable hydrogen molecule inside cannot be suppressed with the low ambient pressure.
PACS: 67.80.ff Molecular hydrogen and isotopes; PACS: 62.50.–p High pressure effects in solids and liquids; PACS: 64.70.K– Solid-solid transitions; PACS: 64.60.Q– Nucleation.