Structure of the Cr³⁺-V₀ Centers in WO₃

The Cr3+-oxygen-vacancy pair center, Cr3+-V0, in WO3 recently observed with EPR by Hirose and Kawaminami is analyzed using the Müller-Berlinger superposition model for Cr3+ as a basis. The large near-axial, ground-state splittings of 2.4 and 2.8 cm−1 at 300 K are accounted for by displacements of 0.12 to 0.18Å of the Cr3+ towards the oxygen vacancy, and distances of 1.90Å to the next four O2− ions. The structure is practically the same as that of the Fe3+-V0 center deduced earlier. The low-temperature splittings of Cr3+-V0 reported are also discussed. © 1986, THE PHYSICAL SOCIETY OF JAPAN. All rights reserved.