Covalent Si–H Bonds in the Zintl Phase Hydride CaSiH1+x (x ≤ 1/3)

Inorganics

Alexandra Franz¹  ThomasC. Hansen²  Henry Auer³  Fangshun Yang³  Holger Kohlmann³  HelenY. Playford⁴ 

[1] Helmholtz-Zentrum Berlin, Hahn-Meitner-Platz 1, 14109 Berlin, Germany;Institut Laue-Langevin, 71 avenue des Martyrs, 38000 Grenoble, France;Institute of Inorganic Chemistry, Leipzig University, Johannisallee 29, 04103 Leipzig, Germany;The ISIS Facility, STFC Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire OX11 0QX, UK;

关键词: Zintl phase;    Zintl phase hydride;    metal hydride;    neutron diffraction;    Rietveld refinement;    pair distribution function;    polyanions;    hydrogen storage;    silicon;    in situ;   

DOI  :  10.3390/inorganics7090106

来源: DOAJ

【 摘 要 】

The crystal structure of the Zintl phase hydride CaSiH_≈4/3 was discussed controversially, especially with respect to the nature of the silicon-hydrogen interaction. We have applied X-ray and neutron powder diffraction as well as total neutron scattering on a deuterated sample, CaSiD_1.1. Rietveld refinement (CaSiD_1.1, Pnma, a = 14.579(4) Å, b = 3.8119(4) Å, c = 11.209(2) Å) and an analysis of the neutron pair distribution function show a silicon-deuterium bond length of 1.53 Å. The Si−H bond may thus be categorized as covalent and the main structural features described by a limiting ionic formula Ca²⁺H⁻(Si⁻)_2/3(SiH⁻)_1/3. Hydrogen atoms decorating the ribbon-like silicon polyanion made of three connected zigzag chains are under-occupied, resulting in a composition CaSiH_1.1. Hydrogen-poor Zintl phase hydrides CaSiH_<1 with hydride ions in Ca₄ tetrahedra only were found in an in situ neutron diffraction experiment at elevated temperature. Hydrogen (deuterium) uptake and release in CaSiD_x (0.05 ≤ x ≤ 0.17) is a very fast process and takes less than 1 min to complete, which is of importance for possible hydrogen storage applications.

【 授权许可】

Unknown