Deuterium-induced copper pairing in Zr2CuD(approximately 5)

Deuteration of Zr2Cu leads to a reconstruction of its MoSi2-type metal atom arrangement. While the tetragonal alloy contains isolated copper atoms (Cu-Cu = 3.22 angstroms) in a cubic zirconium atom environment, the monoclinic deuteride Zr2CuD4.71 contains Cu2 dumbbells (Cu-Cu = 2.39 angstroms), of which each copper atom has a trigonal-prismatic zirconium atom environment. Deuterium occupies five sites, of which four have tetrahedral metal configurations (two Zr4-type and two Zr3Cu-type) and are fully occupied while one has a trigonal-bipyramidal metal configuration (Zr3Cu2-type) and is partially occupied (71%). Copper is bonded to four deuterium atoms in a saddle-like configuration (Cu-D = 1.73-1.87 angstroms). Two of the ligands connect copper in a nearly linear Cu-D-Cu arrangement to partially interrupted dimeric Cu2D6](n)() ribbons running perpendicular to the Cu2 dumbbell direction. At the upper phase limit, the ribbons are presumably no longer interrupted and the deuteride can be described by the limiting ionic formula 2Zr2+Cu(+)D3](2-)2D-.