Europium–Hydrogen Bond Distances in Saline Metal Hydrides by Neutron Diffraction

Abstract

Europium–hydrogen bond distances in saline metal hydrides have been refined from neutron powder diffraction data on the magnesium-based ternary deuterides EuMg₂D₆, EuMgD₄, Eu₂MgD₆, Eu₆Mg₇D₂₆ and Eu₂Mg₃D₁₀. Absorption effects were attenuated by choosing neutron energies close to the minimum absorption cross section of natural isotope mixtures of europium and by using annular sample holders on high-flux neutron diffractometers. Some structures required joint refinements of neutron and synchrotron diffraction data. The Eu-D distances found for the various coordination numbers of europium range between 237–276 pm (CN=9), 220–287 pm (CN=10), 239–287 pm (CN=11) and 228–299 pm (CN=12). They are closely similar to, but shorter by about 4 pm than the corresponding Sr–D distances in strontium analogues, thus underlining the analogy between the europium and alkaline-earth hydride chemistry.