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 the
6 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
Structures of Ionic Solids Based on CCP Structures of Ionic Solids Based on CCP Examples of Structure Adoption Complexion Variants ery common, Most alkali halides(CsCl, CsBr, Csl Nacl Variants MMost oxides chalcogenides of alkaline earths I TiC, NaH CaF (Fluorite) fLuorides of large divalent cations, chlorides of Sr, Ba dOxides of large quadrivalent cations (Zr, Hf, Ce, Th, U) Nao(Anti- Fluor Fes, Pyrite Sro ZnS (Zinc Blende sphale dFormed from polarizing Cut, Ag, Cd=, Ga*.and Polarizable Anions (I-S2 电g.Cu(F,CLBr,D,Ag, S, p ' e), Ga(P As), Hg(S Se, Te) Structures of lonic solids based on hcp Hexagonal Zinc Sulfide(Wurtzite) ZnS Wurtzite Structure 4 CHCP S- with Zns in half Tetrahedral holes (only T+ forT- filled LAttice: Hexagonal otif2sat(0,0.0)&64H12);2Zn at6y&(009 zNs in unit cell cOordination 4: 4(tetrahedraL Structures of Ionic Solids Based on HCp POLYHEDRAL REPRESENTATIONS ZnS Wurtzite PLAN VIEWS 44 n of wurtzite I and Zinc Blende Zinc Blende Wurtzite ettedunted tetthedraon but lares soned in rtte a ect n blade
7 Examples of Structure Adoption NaCl (Halite) Very common, Most alkali halides (CsCl, CsBr, CsI excepted) Most oxides / chalcogenides of alkaline earths Many nitrides, carbides, hydrides (e.g. ZrN, TiC, NaH) CaF2 (Fluorite) Fluorides of large divalent cations, chlorides of Sr, Ba Oxides of large quadrivalent cations (Zr, Hf, Ce, Th, U) Na2O (Anti-Fluorite) Oxides /chalcogenides of alkali metals ZnS (Zinc Blende/Sphalerite) Formed from Polarizing Cations (Cu+ , Ag+ , Cd2+, Ga3+...) and Polarizable Anions (I- , S2- , P3- , ...); e.g. Cu(F,Cl,Br,I), AgI, Zn(S,Se,Te), Ga(P,As), Hg(S,Se,Te) Structures of Ionic Solids Based on CCP Complex-ion Variants Structures of Ionic Solids Based on CCP Hexagonal Zinc Sulfide (Wurtzite) Structure HCP S2- with Zn2+ in half Tetrahedral holes (only T+ {or T- } filled) Lattice: Hexagonal Motif: 2S at (0,0,0) & (2 / 3 , 1 / 3 , 1 / 2 ); 2Zn at (2 / 3 , 1 / 3 , 1 / 8 ) & (0,0,5 / 8 ) 2ZnS in unit cell Coordination: 4:4 (tetrahedral) C6v group Structures of Ionic Solids based on HCP ZnS Wurtzite Structures of Ionic Solids Based on HCP ZnS Wurtzite Comparison of Wurtzite and Zinc Blende
Some Semiconductors Structure Descriptions of Structures With CCP anion array Rock salt, NaCl O occupied Zinc blende. Zns T,(or T_) occupied Antifluorite, Na o T+ and T_ occupied With HCP anion array: Wurtzite ZnS T, or T occupied as6.471 With CCP cation array Very long sequences(several hundred layers, say 500A Structure of Multicomponent Compound in the repeat unit) have been observed in some polytypic aterials (causing by screw dislocations) Derived from zincblende and wurtzite The simplest Polytypism ABAB.and… ABCABO…. two polytypes Superlattice Z Ordered HCP Superlattice Barone Beeley Superlattice Structure of CuFeS and znSnAs Structures of lonic solids based on hcp NiAs CuFeS,: tetragonal system, Nickel Arsenide lattice constant c≈2a ZnSnAs, exist as ordered CuFesa structure at room ∵三 .HCP As with Ni in all Octahedral holes Lattice: Hexagonal-P e, O. s These structures are called ZnS otf2Niat(0,00)&00,y2),2Asat(2)&l2) derivative. They are ordered superlattices. Coordination: Ni 6 (octahedraL: As 6 (trigonalprismatic)
8 Some Semiconductors Structure III-V group II-VI group Compound Crystal Structure Lattice Constant（Å） Compound Crystal Structure Lattice Constant（Å） BN zincblende zincblende a=5.406 AlP zincblende a=4.462 ZnS wurtzite a=3.821, c=6.257 AlAs zincblende a=5.662 ZnSe zincblende a=5.667 AlSb zincblende a=6.136 zincblende a=6.101 zincblende a=4.100 ZnTe GaN wurtzite a=3.814,c=6.257 wurtzite a=3.18,c=5.17 zincblende a=5.818 GaP zincblende a=5.451 CdS wurtzite a=4.136 c=6.713 GaAs zincblende a=5.653 CdSe wurtzite a=4.299, c=7.010 GaSb zincblende a=6.095 CdTe zincblende a=6.471 InP zincblende a=5.869 HgTe zincblende a=6.420 InAs zincblende a=6.058 InSb zincblende a=6.479 Descriptions of Structures With CCP anion array: Rock salt, NaCl O occupied Zinc Blende, ZnS T+ (or T- ) occupied Antifluorite, Na2O T+ and Toccupied With HCP anion array: Wurtzite, ZnS T+ (or T- ) occupied With CCP cation array: Fluorite, ZrO2 T+ and Toccupied Very long sequences (~several hundred layers, say 500 Å in the repeat unit) have been observed in some polytypic materials (causing by screw dislocations). The simplest Polytypism is … ABAB… and … ABCABC… two polytypes B A C B A HCP CCP Structure of Multicomponent Compound Derived from Zincblende and Wurtzite Zincblende Wurtzite CuFeS2 CuSbS2 AgGeTe2 CuFe2S3 Ordered superlattice Cu2SnFeS4 Cu3AsS4 MgGeP2 a-AgInS2 ZnSnAs2 Cu2GeS3 Disordered Superlattice Cu2SnTe3 Cu3SbS3 b-Cu2HgI4 b-Ag2HgI4 Ordered Defected Superlattice In2CdSe4 CuSiP3 Al2ZnS4 a-Ag2HgI 4 a-Cu2HgI4 Disordered Defected Superlattice Ga2HgTe4 Structure of CuFeS2 and ZnSnAs2 vCuFeS2：tetragonal system, lattice constant c » 2a vZnSnAs2 exist as ordered CuFeS2 structure at room temperature, when temperature increased, Zn and Sn array disorderly, which make its structure identical to cubic ZnS structure。 vThese structures are called ZnS derivative. They are ordered superlattices. Structures of Ionic Solids Based on HCP NiAs Nickel Arsenide Coordination HCP As with Ni in all Octahedral holes Lattice: Hexagonal - P a = b, c =(8/3)a Motif: 2Ni at (0,0,0) & (0,0,1 / 2 ), 2As at (2 / 3 , 1 / 3 , 1 / 4 ) & (1 / 3 , 2 / 3 , 3 / 4 ) 2NiAs in unit cell Coordination: Ni 6 (octahedral) : As 6 (trigonalprismatic)