High-pressure phase transition of AB3-type compounds: case of tellurium trioxide

TL;DR

This study combines experimental Raman scattering and DFT calculations to investigate high-pressure phase transitions in tellurium trioxide, revealing a predicted structural change at pressures above 66 GPa and analyzing its electronic properties.

Contribution

It provides the first combined experimental and theoretical analysis of TeO3 under high pressure, predicting a new phase transition and structural stability limits.

Findings

VF3-type structure persists up to 110 GPa experimentally.

Theoretical models predict a transition to YF3-type at 66 GPa.

YF3-type phase remains stable up to 220 GPa before transforming again.

Abstract

Tellurium trioxide, TeO3, is the only example of a trioxide adopting at ambient conditions the VF3-type structure (a distorted variant of the cubic ReO3 structure). Here we present a combined experimental (Raman scattering) and theoretical (DFT modelling) study on the influence of high pressure (exceeding 100 GPa) on the phase stability of this compound. In experiment the ambient-pressure VF3-type structure (R-3c symmetry) is preserved up to 110 GPa. In contrast, calculations indicate that above 66 GPa the R-3c structure should transform to a YF3-type polymorph (Pnma symmetry) with the coordination number of Te6+ increasing from 6 to 8 upon the transition. The lack of this transition in the room-temperature experiment is most probably connected with energetic barriers, in analogy to what is found for compressed WO3. The YF3-type phase is predicted to be stable up to 220 GPa when it should transform to a novel structure of R-3 symmetry and Z = 18. We analyse the influence of pressure on the band gap of TeO3, and discuss the present findings in the context of structural transformations of trioxides and trifluorides adopting an extended structure in the solid state