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

The rare earth vanadate TbVO4, undergoes a crystallographic phase transition below 33 K induced by a cooperative Jahn-Teller effect. Twinning of the crystal occurs upon this transition from the tetragonal high temperature phase to the orthorhombic low temperature phase resulting in a domain structure. Single crystal x-ray analyses of the tetragonal and the twinned orthorhombic phase verify a reduction in the site symmetry of the Tb ion from D2d (m2-dodecahedral) for the high temperature phase to D2 (222-distorted dodecahedral) for the low temperature phase. Concomitantly, the space group symmetry is lowered from D194h (I41/amd) to D242h (Fddd). The twinned orthorhombic phase is described as domains related to each other by a 180? rotation about the orthorhombic [110] axis.