Using first-principles evolutionary simulations, we have systematically investigated phase stability in the Hf-O system at pressure up to 120 GPa. New compounds Hf5O2, Hf3O2, HfO and HfO3 are discovered to be thermodynamically stable at certain pressure ranges and two new high-pressure phases are found for Hf2O: one with space group Pnnm and anti-CaCl2-type structure, another with space group I41/amd. Pnnm-HfO3 shows interesting structure, simultaneously containing oxide O2- and peroxide [O-O]2- anions. Remarkably, it is P-62m-HfO (it is built by a 3D-framework of short and strong Hf-O bonds, reinforced by rather strong Hf-Hf bonds) rather than OII-HfO2 that exhibits the highest mechanical characteristics among Hf-O compounds. Pnnm-Hf2O, Imm2-Hf5O2, P31m-Hf2O and P-4m2-Hf2O3 phases also show superior mechanical properties, these phases can be quenched to ambient pressure and their properties can be exploited.

Pressure induced novel compounds in the Hf-O system from first-principles calculations

251st National Meeting (2016)

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