Hydrogen location and diffusion in a two-dimensional metal: Proton magnetic resonance in metallic zirconium monohalide hydrides

Proton magnetic resonance has been studied in a new class of metal-hydrogen systems, ZrXH, based on the metallic double-layered monohalides of zirconium, ZrCl and ZrBr. The rigid lattice second moments of the proton resonance show that in the hemihydride phases hydrogen predominantly occupies alternate chains of tetrahedral sites within the double layer of close-packed Zr atoms. In the monohydrides all tetrahedral sites are occupied by hydrogen. Activation energies for hydrogen diffusion within the layers are derived from the temperature dependence of the resonance linewidth. A substantial anisotropy of the proton resonance shape is observed at high temperatures.