Hydrogen reduction of ruby at high pressure: Implication for claims of metallic hydrogen

Abstract

We show that the reaction ${\mathrm{Al}}_{1/2}$ ${\mathrm{O}}_3$+3/${4\mathrm{H}}_2$⇆3/2AlOOH+1/2Al proceeds to the right at 300 K and at pressures above 136 GPa, producing the metal aluminum in the process. The system of neighboring particles of ${\mathrm{Al}}_2$ ${\mathrm{O}}_3$ coated with aluminum hydroxide oxide and covered with aluminum is a dc conductor and exhibits a resonance in the infrared which appears as a plasma edge. In view of this, claims of production of metallic hydrogen based on reflectivity studies on composite ${\mathrm{Al}}_2$ ${\mathrm{O}}_3$-${\mathrm{H}}_2$ samples are unwarranted.