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.
@article{arxiv.1509.00326,
title = {Pressure induced novel compounds in the Hf-O system from first-principles calculations},
author = {Jin Zhang and Artem R. Oganov and Xinfeng Li and Kan-Hao Xue and Zhenhai Wang and Huafeng Dong},
journal= {arXiv preprint arXiv:1509.00326},
year = {2015}
}