NMR in the silicon clathrate compounds NaxBaySi46 and NaxSi136

Type I Clathrates as Novel Silicon Anodes: An Electrochemical and Structural Investigation

“…NMR shifts for insulating and tetrahedrally coordinated Si compounds usually occur from 0 to −130 ppm, but large positive shifts are observed in silicon clathrates due to the contribution of electrons from the guest atoms to the conduction band . Although the three crystallographic Si sites (Figure ) can often be distinguished with 29 Si NMR in unsubstituted type I clathrates, the NMR spectra for ternary clathrates often show one or two broad peaks . The reason for the difference in 29 Si chemical shifts between the thermally annealed and Ar arc‐melted clathrate is not yet understood.…”

K7.62(1)Si46 and Rb6.15(2)Si46: Two Structure I Clathrates with Fully Occupied Framework Sites

“…This results in the observed metallic conductivities and also gives rise to large Knight-like Si NMR shifts for framework atoms, reminiscent of metals (38,44,48,49). It is also possible to understand the vacancy formation in terms of a simpli"ed band picture (Fig.…”

Inorganic clathrate-II materials of group 14: synthetic routes and physical properties

“…The electronic structure of several clathrate-II phases has been studied employing nuclear magnetic resonance techniques. 1,83,102,103,113,[116][117][118][119] One feature common to several clathrate-II materials is the relatively large NMR shifts for both the guest and framework species. These shifts have been interpreted as akin to the Knight shifts in metals, originating in the hyperfine interactions between the NMR nuclei and the delocalized conduction electrons.…”