Crystal structure of the clathrates Rb8ln8Ge38 and K8ln8Ge38

Cs8−xSi46: A Type‐I Clathrate with Expanded Silicon Framework

“…In ternary type-I clathrates, like Rb 8 Ga 8 Si 38 , [2] the valence electrons of the alkali-metal atoms are formally transferred to E13 atoms which are transformed into four-bonded anions, in agreement with the 8-N Zintl count. [3] Following this, a hypothetical silicon allotrope with empty clathrate-I structure, SiA C H T U N G T R E N N U N G (cP46), is predicted to be semiconducting.…”

“…The elongation might also be taken as an indication for an inhomogeneous charge distribution in the Si 46 framework. On the other hand, long Si À Si distances have been reported for molecules with bulky protective groups, e.g., in hexa-tert-butyldisilane (tBu 3 Si) 2 , a Si À Si bond length of 2.69 is observed. [22] The average Si À Si distance in Cs 7.…”

Energetic Stability and Thermoelectric Property of Alkali-Metal-Encapsulated Type-I Silicon-Clathrate from First-Principles Calculation

“…In addition, as shown in next section, it was found that the effect of different configurations of the substitutional atom on the thermoelectric properties was negligible. Moreover, the lowest energy configuration obtained in the present study is more stable than the one calculated by Imai et al 15) by 0.21 eV/f.u., where the previous experimentally determined occupancy 37,40) was used. On the basis of the above result for the stable configurations of substitutional atoms, the formation energies of X 8 Y 8 Si 38 per chemical formula were calculated and are shown in Fig.…”

Ternary Compounds in the Sn-Rich Section of the Ba–Ga–Sn System: Ba8Ga16–xSn30+x (1.1 ≤ x ≤ 2.8) Clathrates of Type-I and Type-VIII, and BaGa2–xSn4+x (x ≈ 0.2) with a Clathrate-like Structure

“…The zeolitic framework ( Figure 6) is made up of large (Ga,Sn) 18 polyhedra with 7 faces (6 2 6 2 6 1 8 2 ), shown in red in the figure. They are face-shared to form layers running parallel to the (001) plane, which are separated by layers of fused (Ga,Sn) 9 cages. The large (Ga,Sn) 18 polyhedra encapsulate the Ba atoms (site 4c), while the smaller cages are empty.…”

“…A possible solution to this synthetic problem can be based on the fact that the polyhedra in the clathrates' structures are of quite different dimensions. Implementation of this idea allows for the rational synthesis of the clathrate type-II compounds (Cs or Rb) 8 Na 16 (Si or Ge) 136 [5,6] and (Cs or Rb) 8 Na 16 (Ga,Si) 136 [7]-ratio of 24:136 or 1:5.67-instead of the analogous clathrates type-I compounds Na 8 Si 46 [8] or Rb 8 Ga 8 Ge 38 [9]-ratio of 8:46 or 1:5.75-where the two cavities are closer in size.…”