Cooperative Jahn-Teller induced phase transition of TbVO4: single crystal structure analyses of the tetragonal high temperature phase and the twinnedorthorhombic phase below 33 K

The rare earth vanadate TbVO4, undergoes a crystallographic phase transitio n below 33 K induced by a cooperative Jahn-Teller effect. Twinning of the c rystal occurs upon this transition from the tetragonal high temperature pha se to the orthorhombic low temperature phase resulting in a domain structur e. Single crystal x-ray analyses of the tetragonal and the twinned orthorho mbic phase verify a reduction in the site symmetry of the Tb ion from D-2d ((4) over bar m2-dodecahedral) for the high temperature phase to D-2 (222-d istorted dodecahedral) for the low temperature phase. Concomitantly, the sp ace group symmetry is lowered from D-4h(19) (I4(1)/amd) to D-2h(24) (Fddd). The twinned orthorhombic phase is described as domains related to each oth er by a 180 degrees rotation about the orthorhombic [110] axis.