Mechanism of the transition of solid hydrogen to the conducting state at high pressures

The density functional theory is applied for the calculation of the dependence of pressure and profiles of proton–proton pair correlation function of hydrogen on density in the range 1.14–2.0 g/cm³ at temperature 100 K. The calculated range of pressures is 300–2600 GPa, which corresponds to the solid phase of hydrogen. The transition at pressure 607 GPa is found, which is characterized by a noticeable jump of electrical conductivity and a sharp decrease in the number of molecules of H₂. The structural transition is characterized by the first peak of the pair correlation function at a distance of 0.92 Å, which corresponds to the interatomic distance in the ion ${{\rm{H}}}_{3}^{+}$ and does not depend on density. Therefore, the nature of the transition combines ionization with structural changes.