Cubic 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. 

Crystalline diamond structure parameters cubic syngony with a = 3.55 A. 

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. 

The cubic system does not allow a cell of C (A,B) type because the centering of only two opposite faces cancels the 4 axes ofA characteristic to the syngony, contrary to the a) condition above. 

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