Location of deuterium inα-scandium

Abstract

Neutron-diffraction techniques have been used to study the location of deuterium in a single crystal of $\mathrm{Sc}{\mathrm{D}}_x$ ($x=0.33\mathrm{}$; measured cell parameters: $a=3.338\mathrm{}\pm 0.002$ Å and $c=5.299\mathrm{}\pm 0.008$ Å). To compare under identical conditions the thermal factors of Sc in $\mathrm{Sc}{\mathrm{D}}_x$ to those of pure Sc, measurements were also performed on single crystals of pure Sc (cell parameters: $a=3.3088\mathrm{}\pm 0.0002$ Å and $c=5.2680\mathrm{}\pm 0.0003$ Å). The integrated reflectivities of forty reflections (with $\frac{sin\theta }{\lambda }\lesssim 0.7$ ${\mathrm{\AA }}^{-2\mathrm{}}$) of both $\mathrm{Sc}{\mathrm{D}}_x$ and pure Sc were measured at room temperature. We find that the deuterium atoms in $\mathrm{Sc}{\mathrm{D}}_x$ occupy, within the limits of experimental precision, the tetrahedral sites of the host lattice, a result in contradiction with that obtained in a NMR study of this system. The temperature factors of Sc in pure Sc and in $\mathrm{Sc}{\mathrm{D}}_x$ were found to agree to within experimental precision. This observation indicates that the addition of deuterium does not appreciably affect the low-frequency vibrational modes of the host metal.