DIMERIZATION OF CUGEO3 IN THE SPIN-PEIERLS STATE

The dimerization of the Cu ions in the spin-Peierls state of CuGeO3 be low 14 K has been determined by neutron-diffraction measurements. In a ddition to superlattice reflections with indices h/2kl/2 (h, k, l, all odd) recently observed in electron and x-ray diffraction studies, we also found peaks for which k = even. Oxygen displacements in the a-b p lane of about 0.01 angstrom, accompanied by comparable shifts of the C u ions along the chain direction c, can be related to the dimerized sp in state in a natural fashion.