Location of deuterium inα-yttrium

Neutron-diffraction techniques have been used to assess the deuterium location in a single crystal of $\alpha$-yttrium. We find that in the $\alpha$ phase of $\mathrm{Y}{\mathrm{D}}_x\mathrm{}(x=0.176\mathrm{})\mathrm{}$ the deuterium atoms occupy predominantly the tetrahedral sites of the hcp lattice. The isotropic temperature factor of yttrium, obtained in the present experiment, is found to be smaller than that of pure yttrium. This result indicates that the addition of deuterium hardens the phonon frequency spectrum of the host metal.