Deuterium site energy difference in ZrTi2D4.3 as studied by high-temperature neutron diffraction

The deuterium atom distribution in the deuterium stabilized C15-type Laves phase derivative ZrTi2D4.3 has been studied by neutron powder diffraction in the temperature range 300 K < T < 1000 K. As the temperature is increased the occupancy of the tetrahedral ZrTi3-type interstices decreases from 89% at 300 K to 56% at 800 K while that of the tetrahedral Zr2Ti2-type interstices increases from 7% to 17%. The deuterium site energy difference derived from these data is ∼127 meV. Above 800 K the compound loo\ses deuterium mainly from the ZrTi3-type interstices while its metal atom substructure becomes partially disordered. This disorder persists after cooling to room temperature.