A single crystal neutron diffraction investigation of diopside at 10 K

Single-crystal neutron-diffraction data, collected at 10 K on a natural sample of diopside, provided a structure that refined to R = 4.5% for 415 independent reflections. The structure refinement showed significant reduction of the M(2)-O(3C2),(3D2) bond lengths, resulting in a more regular M(2) polyhedron than at higher temperatures. A significant zero-point contribution to the atomic displacement parameters (ADP) was found. On average, it accounts for the 35% of the room-temperature determination. Such results confirm previous predictions based on lattice-dynamics calculations.