Ge₃₈P₈I₈ and Ge₃₈As₈I₈, a New Class of Compounds with Clathrate Structure

On the crystal structure of the germanium-based cationic clathrates [Ge38.3Sb7.7]I7.44, [Ge38.1P7.9]I8, and [Ge30.5Sn7.7P7.75]I7.88

“…The host framework sub structure reveals no vacancies or positional disorder, so that the crystal structure of the reported compounds is close to the ideal one of clathrate I. However, there is a certain specificity in the distribution of atoms within the framework (Table 5), which has essential differ ences as compared to a group of the already men tioned cationic clathrates [Ge 38 Pn 8 ]X 8 [13][14][15][16]. The latter compounds were found to have a full occupancy of all sites and a complete separation of germanium and pnictogen atoms.…”

“…We re vealed no deviations from the space group Pm n, such as superstructure formation or lowering of the symme try, in spite of the fact that the non centrosymmetric space group P n was reported for the related com pounds [Ge 38 Pn 8 ]X 8 (Pn = P, As, Sb; X = Cl, Br, I) [13][14][15][16]. Our attempts to solve the crystal structures in other space groups (e.g.…”

“…Besides, there is a smaller family of clathrates with the inverse host guest polarity, where halides or tellurium appear as guest anions in the positively charged framework. For the first time these compounds with the general for mulae [Ge 38 Pn 8 ]X 8 (Pn = P, As, Sb; X = Cl, Br, I) were reported by Menke and von Schnering [13][14][15][16]. They reported all these compounds to crystallize in the non centrosymmetric analog of the group Pm n, the space group P n, which was (in part) questioned later [17].…”

“…Given the recent interest into clathrates as potential thermoelectric materials [20,21] and the great influence of the fine structural details on the transport properties of these compounds, we per formed the detailed reinvestigation of the crystal structures of the [Ge 38 Pn 8 ]I 8 family [13][14][15][16] [14,15]. The latter compound was previously unknown.…”

Synthesis, Structure, and Properties of Clathrate Si30.3(8)P15.7(8)Se7.930(3)

“…[1] The discovery of Na 8 Si 46 led to the era of intermetallic and semiconducting clathrates; [2] since then,t hermoelectric, [3][4][5] superconducting, [6] and ferromagnetic [7][8] properties have been found in clathrates. [1][2][3][4][5][6][7][8][9][10] Alternatively,t he cationic clathrate framework is positively chargeda nd traps halides, [12][13][14] tellurium, or selenium [15][16][17][18] anions. [9] Although several structure types have been discovered, [10] the majority of clathrates belong to the clathrate-I structure type with the cubic space group Pm3 n. The clathrate-I structure features at hree-dimensional host framework that is based on the group 13, 14, and 15 elements, which encapsulates the guest atoms in large cavities.S trong covalentb onds exist within the framework structure, whereas the guest atoms are held within the framework cavities by weaker interactions.…”