Crystal 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. 

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. 

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. 

SmE D2 X T(0) Biaxial crystal with upright molecules having true three- dimensional positional order. Rectangular in-plane lattice and herringbone packing of molecules (orthorhombic syngony). Soft crystal with small shear elastic modulus... 

The lattice types are labeled by P (simple or primitive), F (face-centered), I (body-centered) and A B,C) (base-centered). Cartesian coordinates of basic translation vectors written in units of Bravais lattice parameters are given in the third column of Table 2.1. It is seen that the lattice parameters (column 4 in Table 2.1) are defined only by syngony, i. e. are the same for all types of Bravais lattices with the point symmetry F and all the crystal classes F of a given syngony. 

Syngony F° -crystal classes F Direct lattice types Basic translation vectors Bravais lattice par am. 

Correlations between the translation vector length and the angles between them define possible crystal classes or syngony, resulting from the unit cell form and the crystal lattice. There are seven crystal classes (or syngony), plotted in Table 9.1. 

---