High-pressure phase transition of AB(3)-type compounds: case of tellurium trioxide

Tellurium trioxide, TeO(3), is the only example of a trioxide adopting at ambient conditions the VF(3)-type structure (a distorted variant of the cubic ReO(3) 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 experiments the ambient-pressure VF(3)-type structure (R3̄c symmetry) is preserved up to 110 GPa. In contrast, calculations indicate that above 66 GPa the R3̄c structure should transform to a YF(3)-type polymorph (Pnma symmetry) with the coordination number of Te(6+) 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 WO(3). The YF(3)-type phase is predicted to be stable up to 220 GPa when it should transform to a novel structure of R3̄ symmetry and Z = 18. We analyse the influence of pressure on the band gap of TeO(3), and discuss the present findings in the context of structural transformations of trioxides and trifluorides adopting an extended structure in the solid state.