Synthesis and crystal structure of -Zr9V4SH∼23

The Zr 9 V 4 SH ∼23 hydride was synthesized by saturation from gaseous hydrogen at room temperature and 0.12 MPa hydrogen pressure. The measured hydrogen absorption capacity of the κ -Zr 9 V 4 S was 1.77 H/M. The refinement of the hydride structure with the use of X-ray powder diffraction data confirmed the preserved symmetry of the metallic matrix (sp.gr. P 6 3 / mmc , a = 9.2715 ( 2 ) , c = 9.0756 ( 4 ) A , Δ a / a = 7.3 % , Δ c / c = 6.1 % , Δ V / V = 22.1 % , Δ V / at.H = 2.62 A 3 ). The analysis of interstices in this compound revealed that without positioning hydrogen atoms in triangular Zr 3 interstices it is impossible to model the structure of k -hydride with the experimentally observed capacity. Neutron powder diffraction study of the Zr 9 V 4 SD ∼23 deuteride (sp.gr. P 6 3 / m m c , a = 9.2779 ( 5 ) , c = 9.0779 ( 5 ) A) revealed deuterium atoms filling two tetrahedral and three triangular interstices. A full occupancy of only one site (D4) was observed in our sample giving the refined deuterium content of 20.8(2) D/f.u. Filling of the D4 site causes a displacement of the sulphur atoms from the three-fold axis (splitting of 2c to 6h position).