Condensed Modes of WO₃ Represented by the Normal Modes in the Space Group D_4h⁷

抄録

The prototypic phase of WO₃ is considered to be the tetragonal phase with the space group D_4h⁷, that is the highest temperature phase, to explain systematically the displasive successive phase transitions of WO₃.
The normal modes at the points Γ, Z, M and A in the tetragonal Brillouin zone are studied with the help of the group theory and are compared with the normal modes in the cubic WO₃ that is the hypothetic prototype with the space group O_h¹.
The condensed modes in each phase of WO₃ are described by the irreducible representations of the normal modes in the tetragonal WO₃, referring to the results of X-ray and neutron diffraction studies.