Syngony

The compound Li4Nb04F crystallizes in cubic syngony, with a cell parameter of 4.192 A and a Rock Salt (NaCl) structure. The compound s X-ray diffraction pattern and cell parameter are very similar to those of nickel oxide, NiO. 

Compound Syngony Cell parameters, A a b c a P Z Space Group Density p, g/cm3 Reference... 

The only known compounds that contain trivalent metals are heptaluoroniobates (TV) of lantanides - LnNbF7. Such compounds crystallize in monoclinic syngony, and have an LnZrF7 type structure. 

The compound Ag(TaF6)2 crystallizes in triclinic syngony with cell parameters (A, grad.) as follows a = 9.061, b = 5.607, c = 5.207, a = 118.7, p = 91.61, y = 102.3. Ag(TaF6)2 is composed of two separate layers made up of octahedral ions AgF64 and distorted octahedral complexes NbFe that are linked through the planes. 

According to investigations [215], the structure of Marignac s salt corresponds to the formula K2Ta203F6. The compound crystallizes in orthorhombic syngony, with a space group of Pnma - D, Z = 4. 

Table 32. Structural characteristics of M Ta OsFf, compounds (M = NH4, K, Rb) and Cs7TasOnF2i, with 4 < X Me<5 (all compounds have orthorhombic syngony).

CoNbOF5 [129] can also be considered an MeX3 type compound due to the steric similarity of cobalt and niobium ions. This compound crystallizes in tetragonal syngony with cell parameters a = 7.81 and c = 9.02 A (Z = 4 p = 3.19 g/cm3), and can be considered to have a distorted cubic Re03 structure. Both cobalt and niobium occur in the center of oxyfluoride octahedrons that are linked via their vertexes. 

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