Lithium metal atoms fill vacancies in the germanium network of a type-I clathrate: synthesis and structural characterization of Ba₈Li₅Ge₄₁

Abstract

Clathrate phases with crystal structures exhibiting complex disorder have been the subject of many prior studies. Here we report syntheses, crystal and electronic structure, and chemical bonding analysis of a...

Yet Another Case of Lithium Metal Atoms and Germanium Atoms Sharing Chemistry in the Solid State: Synthesis and Structural Characterization of Ba2LiGe3

“…[25] Initially, we had no reasonable hypothesis as to why this might be the case, but potential breakthrough came to light when we synthesized and characterized the type-I clathrate Ba 8 Li 5 Ge 41 (or rather Ba 8 Li x Ge 46À x (x < 5.33), where Li/Ge disorder was observed. [27] Our results, based on single-crystal X-ray diffraction work, showed the existence of Li occupying a crystallographic site nominally taken by Ge. This shared chemistry between lithium and germanium atoms in the solid state contributes to subtle changes in the unit cell volume and subsequent small peakshifts when experimental and simulated powder X-ray diffraction patterns are compared.…”

“…For the past 6-7 years, we have been studying the lithiation behavior of Ge-based clathrates. [27][28][29] Over the course of our work, we often observed the presence of some of the abovementioned ternaries as reaction byproducts. One particular experimental observation piqued our attention, namely, the small mismatch between the observed and simulated powder X-ray diffraction patterns for Ba 2 LiGe 3 .…”

“…[49] On this note, we will recall that Li atoms replacing Ge atoms in a crystal structure of a solid is a rare phenomenon, but not without precedents. For instance, recently, when we reported on Ba 8 Li 5 Ge 41 (actual chemical formula Ba 8 Li x Ge 46À x (x < 5.33) with the type-I clathrate structure, [27] based on single-crystal Xray diffraction work, we concluded that one of the crystallographic sites nominally taken by Ge (6c) shows co-occupation by lithium atoms that are sharing the chemistry with germanium atoms. While unusual, another example of this kind of Li/ Ge disorder has been seen in the similar type-I clathrate K 8 Li x Ge 44À x/4 & 2À 3x/4 (0 < x < 2.67; & denotes a vacancy).…”

“…As described in the introduction, for a number of years, we have been actively studying the lithiation behavior of BaÀ Ge clathrates. [27][28][29] During the work, we noticed some difficulties with the interpretation of our own experimental results that mostly stem from the fact that the phase space in the BaÀ LiÀ Ge system is not widely explored (thus far). Besides our own recent discovery of the type-I clathrate Ba 8 Li 5 Ge 41 (= Ba 8 Li x Ge 46À x with x � 5), only three other ternary phases with different Ba/Li/Ge ratios have been reported, with the first one discovered in 1996.…”

“…Germanium in a combination with the lightest alkali metal, lithium and the heaviest (non-radioactive) alkaline-earth metal, barium, affords the following BaÀ LiÀ Ge ternary phases: BaLi 2 Ge (isolated Ge 4À anion), [24] Ba 2 LiGe 3 (isolated [Ge 6 ] 10À anion), [25] BaLiGe 2 (cis-trans [Ge 2 ] 3À chain), [26] and Ba 8 Li 5 Ge 41 (open 3D-framework). [27] The structures of Ba 2 LiGe 3 and BaLiGe 2 have no precedent among the respective binary phases.…”