Evolution of hydrogen superstructure with k=(1/2 1/2 1/2) in ZrV2D2+delta,-0.8 <delta < 0.2

We have performed a neutron-diffraction study of the superstructure with k= (1/2 1/2 1/2) in the hydrogen solid solution ZrV2-D and have followed its e volution with hydrogen content at 100 K. The superstructure belongs to the space group Cc and can be characterized by one of the two stoichiometric co mpositions, either ZrV2D1 or ZrV2D3. Its real range of existence is limited from top by the composition ZrV2D2 owing to the short-range hydrogen-hydro gen interaction. An indication of temperature evolution of the superstructu re has been found. (C) 1999 Elsevier Science S.A. All rights reserved.