The CaF (Fluorite) Structure Two Miscellaneous Structural Concepts structuralism f alternating empty Minerals with the same structure, but different and occupied cubes compositions Antistructuralism cations where the other has anions and vice-versa Structures of ionic solids based on ccp ZnS Zinc blende 圈 Locations of in FCc structure ●Ca2 Cubic Zinc Sulfide Structures of Ionic Solids Based on CCP (Zincblende) Structure nS Zinc Blende(Sphalerite) OCCP S2 with Zn2+ in half Tetrahedral holes (only T+ for T-) filled) o4ZnS in unit cell oMotif. S at(0,0,0); Zn at(AIA cOordination 4: 4(tetrahedraL cubic close packing OCation and anion sites are topologically identical ll in half of the6 Two Miscellaneous Structural Concepts Isostructuralism Minerals with the same structure, but different compositions CaF2 - BaCl2 Antistructuralism Minerals with the same structure, but one has cations where the other has anions and vice-versa CaF2 - Na2O The CaF2 (Fluorite) Structure Can be thought of as a 3D array of alternating empty and occupied cubes The CaF2 (Fluorite) Structure ZnS Zinc Blende (Sphalerite) Structures of Ionic Solids Based on CCP Locations of Tetrahedral Holes in FCC Structure Cubic Zinc Sulfide (Zincblende) Structure (FCC S(0,0,0)， Zn(¼, ¼, ¼). Td group (S atoms: cubic close packing， Zn atoms fill in half of the tetrahedral interstitials Structures of Ionic Solids Based on CCP ZnS Zinc Blende (Sphalerite) CCP S2- with Zn2+ in half Tetrahedral holes (only T+ {or T-} filled) Lattice: FCC 4ZnS in unit cell Motif: S at (0,0,0); Zn at (1/4 , 1/4 , 1/4 ) Coordination: 4:4 (tetrahedral) Cation and anion sites are topologically identical