CRYSTAL-STRUCTURE AND SUPERCONDUCTIVITY OF HIGH-PRESSURE HYBRIDES ANDDEUTERIDES OF HFRU AND ZRRU COMPOUNDS

The solubility of hydrogen and deuterium in HfRu and ZrRu was measured at 600 K and pressures up to 7 GPa. HfRuH(D) almost-equal-to 3.6 and ZrRuH(D)1.6-2.2 were synthesized. At ambient pressure these were shown to be superconductors with T(c) almost-equal-to 4.5 and 3 K respectiv ely. No difference between the T(c) values of the hydrides and deuteri des of the same compound was detected. X-ray diffraction at 100 K has shown the metal sublattices of HfRuH(x)(D(x)) and ZrRuH(x)(D(x)) to be base-centred orthorhombic with very similar unit cell parameters. The crystal structures of HfRuH3.6 and HfRuD3.6 determined by neutron dif fraction at 120 K were of the ZrNiH3 type. The observed superconductin g and structural properties of HfRuH(x)(D(x)) and ZrRuH(x)(D(x)) agree with the predictions of the rigid d-band model. The applicability of this model to other high pressure hydrides is discussed.