One-dimensional ordering of deuterium in solution in yttrium

Abstract

Diffuse neutron scattering measurements on a single crystal of alpha -YD0.17 indicate an order-disorder transition between 170 K and 280 K. Above 280 K, a broad ridge of scattering intensity in a plane normal to the (00l) direction at l approximately 4/3 indicates that the deuterons have formed pairs on next-nearest tetrahedral sites along the c direction of the yttrium host lattice. As the temperature is lowered through the transition region, the feature becomes narrower and more intense and shifts somewhat closer to the l=4/3 position. This behaviour can be largely explained by a simple model that assumes a repulsive hard-core plus long-range attractive potential between deuteron pairs along lines in the c direction. As the temperature is reduced these interactions cause the deuterons to arrange themselves in lines along this direction, each line being uncorrelated with all other such lines. The origin of the interaction is presumably electronic and may lie in the nature of the Fermi surface of yttrium.