Structures of AX,AX2 and ABX3 type compounds
The simple structures come from the arrangement of the anions (though sometimes the cations) in the positions of the spheres in the fcc or hcp lattices, and the cations go into some or all of the octahedral and tetrahedral holes within the lattices. Structures based on face centered cubic lattices The Rock Salt structure This the structure adopted by Sodium Chloride , NaCl. It is based on the fcc array of the large chloride anions, and the sodium cations occupy all the octahedral holes in the fcc lattice . However, it could also be seen as an fcc array of sodium ions, with the anions in all the octahedral holes. Each ion is octahedrally coordinated by six counterions, and so this structure has so-called (6,6)-coordination , where the first number refers to the coordination of the cation and the second to the anion . The structure beyond the first coordination sphere can also be visualized. The Rock Salt, or NaCl, structure The sodium c...
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