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

TL;DR

This study uses first-principles calculations to discover new stable Hf-O compounds under high pressure, revealing their structures, electronic properties, and potential for practical applications due to their superior mechanical characteristics.

Contribution

The paper reports the discovery of several new thermodynamically stable Hf-O compounds and a novel high-pressure phase, expanding the understanding of Hf-O system under extreme conditions.

Findings

New stable Hf-O compounds identified at high pressure

HfO and Hf2O phases exhibit semimetallic behavior

Certain phases show superior mechanical properties and can be quenched to ambient conditions

Abstract

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 a new stable high-pressure phase is found for Hf2O with space group Pnnm and anti-CaCl2-type structure. Both P62m-HfO and P4m2-Hf2O3 show semimetallic character. Pnnm-HfO3 shows interesting structure, simultaneously containing oxide O2- and peroxide [O-O]2- anions. Remarkably, it is P62m-HfO rather than OII-HfO2 that exhibits the highest mechanical characteristics among Hf-O compounds. Pnnm-Hf2O, Imm2-Hf5O2, P31m-Hf2O and P4m2-Hf2O3 phases also show superior mechanical properties, these phases can be quenched to ambient pressure and their properties can be exploited.