First principles prediction of new high-pressure phase of InOOH

Abstract

We have predicted a new high-pressure phase of InOOH by first principles density functional calculations, which stabilizes at ∼ 15 GPa under the static 0 K condition. The structure obtained at 15 GPa has a pyrite-type InO₂ framework with the interstitial asymmetric hydrogen bonds, which is assigned to the space group P2₁3 (No. 198). The cell parameters and internal atomic coordinates optimized at 15 GPa are a = 5.265 Å, In_x = 0.005, O1_x = 0.367, O2_x = 0.633, and H_x = 0.487. Relative enthalpies also indicate that the dehydration of this phase into In₂O₃ + H₂O is unlikely to occur at least up to 50 GPa under the static condition. To our knowledge, this is the first report on the high-pressure isochemical phase transition of oxyhydroxide compounds to the pyrite-type structure. The new phase of InOOH has been identified in an experiment, as reported in detail in a separate paper. We have also found that the low-pressure-type asymmetric hydrogen bond in the new pyrite-type phase changes to the symmetric hydrogen bond over 30 GPa. The present results suggest that a similar phase relation is expected in other group IIIB oxyhydroxides such as AlOOH and GaOOH.