ANHARMONIC STRUCTURAL BEHAVIOR IN CUGEO3

The structure of the spin-Peierls system CuGeO3 has been analyzed by n eutron diffraction as a function of temperature up to 490 K. The prono unced temperature dependency of several bond angles reported previousl y is found to increase with increasing temperature. Therefore, it can be excluded that it is due to spin-lattice coupling. However, at low t emperatures additional, much weaker, structural effects occur, which a re clearly induced by a magnetic interaction. The strong distortion re cently proposed for CuGeO3 by Hidaka et al. [M. Hidaka et al., J. Phys . Condens. Matter 9, 809 (1997)] is not found in our crystals neither on a short nor on a long-range scale.