Features of the Jahn-Teller displacements in LaTiO3

Atomic displacements involved in a crystal structure of LaTiO3 have been investigated by means of transmission electron microscopy mainly at room temperature. Electron diffraction patterns taken from LaTiO3 were found to be characterized by the presence of the forbidden reflections for the Pnma structure. The extinction rule of these reflections including fundamental ones indicated that a space group of the crystal structure was determined to be P2(1)/a with a monoclinic symmetry. A characteristic feature of the P2(1)/a structure is that there exist the Jahn-Teller atomic displacement with q = <1/2 1/2 0>(c) as well as the Jahn-Teller distortion. An additional displacement with q = <1/2 0 0>(c) should also be needed. (C) 2002 Elsevier Science Ltd. All rights reserved.