It is believed that within giant planets submitted to pressure 3000 times greater than Earth’s atmospheric pressure, hydrogen can achieve the metallic phase, becoming a solid black. Experiments done in 2002 indicated that hydrogen could become metallic at a pressure of 450 GPa (gigapascals). Physicists at the University of Edinburgh in the United Kingdom, came close to this using diamond anvils to squeeze hydrogen the 325 GPa.
And it seems that they are on the right track: the experiment showed a new phase of hydrogen, called phase V, in which the element starts to exhibit different properties from those found in its gaseous phase.
The molecules of hydrogen (H2) began to crumble, separating into individual atoms, while the electrons of these atoms have already begun to introduce a typical behavior of metals.
More pressure or lithium
The team claims that this phase V is just the beginning of molecular hydrogen separation, and that even greater pressure will be needed to create the pure metallic Atomic state predicted by theory.
First experimental evidence of the metallic hydrogen
On the other hand, in 2009 theoretical physicists presented a proposal which is to reach the metallic hydrogen with the addition of lithium, which could dispense with these colossal pressures, that are difficult to produce and last a short time, making the analysis of the results.