Size Matters: New Zintl Phase Hydrides of <i>RE</i>Ga (<i>RE</i> = Y, La, Tm) and <i>RE</i>Si (<i>RE</i> = Y, Er, Tm) with Large and Small Cations
oleh: Anton Werwein, Thomas C. Hansen, Holger Kohlmann
| Format: | Article |
|---|---|
| Diterbitkan: | MDPI AG 2019-11-01 |
Deskripsi
Many Zintl phases exhibiting a CrB type structure form hydrides. Systematic studies of <i>AeTt</i>H<sub>x</sub> (<i>Ae</i> = Ca, Sr, Ba; <i>Tt</i> = Si, Ge, Sn), <i>LnTt</i>H<sub>x</sub> (<i>Ln</i> = La, Nd; <i>Tt</i> = Si, Ge, Sn), and <i>Ln</i>GaH<sub>x</sub> (<i>Ln</i> = Nd, Gd) showed the vast structural diversity of these systems. Hydrogenation reactions on <i>RE</i>Ga (<i>RE</i> = Y, La, Tm) and <i>RESi</i> (<i>RE</i> = Y, Er, Tm) were performed in steel autoclaves under hydrogen pressure up to 5 MPa and temperatures up to 773 K. The products were analyzed by X-ray and neutron powder diffraction. <i>RE</i>Si (<i>RE</i> = Y, Er, Tm) form hydrides in the <i>C</i>-LaGeD type. LaGaD<sub>1.66</sub> is isostructural to NdGaD<sub>1.66</sub> and shows similar electronic features. Ga-D distances (1.987(13) Å and 2.396(9) Å) are considerably longer than in polyanionic hydrides and not indicative of covalent bonding. In TmGaD<sub>0.93(2)</sub> with a distorted CrB type structure deuterium atoms exclusively occupy tetrahedral voids. Theoretical calculations on density functional theory (DFT) level confirm experimental results and suggest metallic properties for the hydrides.