Structures

• M2X structure is anti-fluorite
• Coordination of M2X is 4:8
• Packing of M2X is CCP
• All tetrahedral holes are filled in anti-fluorite
• Example of M2X is Li2O
• MX structures are zinc blende, wurtzite, rocksalt, nickel arsenide, caesium iodide
• Zinc blende coordination is 4:4
• Zinc blende packing is CCP
• Zinc blende have 1/2 tetrahedral holes filled
• example of zinc blende structure is ZnS
• Coordination of wurtzite is 4:4
• Packing of wurtzite is HCP
• 1/2 tetrahedral holes filled in wurtzite
• example of wurtzite = ZnS
• Coordination of rocksalt structure is 6:6
• packing of rocksalt structure is CCP
• all octahedral holes are filled for rocksalt
• example of rocksalt = NaCl
• nickel arsenide coordination is 6:6
• packing of nickel arsenide is HCP
• All octahedral holes filled for nickel arsenide
• example of nickel arsenide = NiAs
• Coordination of Caesium Iodide is 8:8
• Packing of Caesium iodide is primitive cubic packing of I-
• all cubic holes filled with Cs+ in CsI
• Example for caesium iodide = CsI
• MX2 structures are rutile, distorted rutile and fluorite
• Rutile coordination is 6:3
• Packing of rutile structure is HCP
• 1/2 octahedral holes filled in rutile structure
• example of rutile structure = TiO2
• Coordination of distorted rutile is 6:3
• Packing of distorted rutile structure is HCP
• 1/2 octahedral holes filled for distorted rutile structure
• example of distorted rutile structure is CaCl2
• Coordination of fluorite is 8:4
• packing of fluorite is simple cubic packing of F- ions (Ca2+ fill 1/2 cubic holes) and cubic close packing of Ca2+ ions (F- fill all tetrahedral holes)
• Example of fluorite structure = CaF2
• polarised tetrahedral MX2 has packing ccp of anions with cations in 1/4 tetrahedral holes
• example of polarised tetrahedral MX2 is BeCl2