5 Some Important Crvstal Three Ways to Describe Crystal Structures Structi Why we need to know some ructure 。的小 Structural sketches of P,O, molecules Dion-stacking model: showing O= forms close packing and P (coordination polyhedron model: showing that the connection Gemstone How Can I Tell If My Diamond Is the Real Thing, Not Cubic ZrO2? Three simple way Synthetic ZrO, 2. Density test. Sapphire 3. Fog test Put the rock in front of your mouth and fog it like ou would try to fog a mirror. If it stays fogged for Diamond the heat instantaneously, so by the time you look Garnet Physical Properties of Crystals Form habit a Crystal form habit aForm: directly reflects the underlying atomic g Cleavage fracture structure(bonding, symmetry, etc ).Constant s Hardness interfacial angles a Specific gravity a Luster OHabit: the characteristic way the mineral C grows. Does not always conform to the form e.g e Streak nice perfect crystals, and depends of where grows and how made a Reaction to Acid 8 Other
1 5 Some Important Crystal Structures Why we need to know some important crystal structures? Three Ways to Describe Crystal Structures Three Structural sketches of P4O10 molecules: (a)Stick-ball model：showing that the P-O chemical bond is the tetrahedral coordination and sp3 covalent bonds. (b)ion-stacking model：showing O2- forms close packing and P5+ exists in tetrahedral interstitials. (c)coordination polyhedron model: showing that the connection of the tetrahedral coordination and tetrahedron, and the octahedral interstitials is unoccupied. I Gemstone Sapphire Garnet Topaz Synthetic ZrO2 Diamond Three simple ways: 1.X-ray diffraction. 2.Density test. 3.Fog test: Put the rock in front of your mouth and fog it like you would try to fog a mirror. If it stays fogged for 2-4 seconds, it’s a fake. A real diamond disperses the heat instantaneously ，so by the time you look at it, it has already cleared up. How Can I Tell If My Diamond Is the Real Thing, Not Cubic ZrO2 ? Physical Properties of Crystals Crystal form & habit Cleavage & fracture Hardness Specific gravity Luster Color Streak Taste Reaction to Acid Other… Form & Habit Form: directly reflects the underlying atomic structure (bonding, symmetry, etc.). Constant interfacial angles. Habit: the characteristic way the mineral grows. Does not always conform to the form e.g. nice perfect crystals, and depends of where grows and how made
2D Similarity of NaCl(111) and Urea(111) Epitaxy Growth of Crystal twhen epitaxy growth, both gas and liquid, the match of lattice parameter should be considered 2图包是出盐 For example, in preparation of conducting thin og 099 crystallized from the supersatura =3.82A),the substrate can be the single crystal slice: SrTiO(100).a=3.91A aortio of unres aue te growth slowe than that of NaCl (100) dn hydrothermal deposition of TiO, thin film aThe 2D similarity of crystal Si(100), the lattice parameter of TiO structure cause such phenomena. b=10917A,d12=2a(a=543A,2a=1 0, so grow TiOg thin film with high 112 orientation. Carbon Allotropes Graphite Carbon shows both Layer and Cage Networks Graphite&s 2各 Diamond Sphalerite (ZnS)vs Diamond Structure Diamond hybrid C Ta group strongest/hardest material 深x known shows us the 4-fold coordination in bot High thermal conductivity (unlike ceramics) structures Transparent in the visible and infrared with high index of refraction Semiconduct doped to make devices Metastable (transforms to see the“ diamond carbon when heated)
2 2D Similarity of NaCl(111) and Urea(111) (3 Cl- constitute equilateral triangle; 3 urea molecules constitute triangle. Compare the two triangles,the lateral length of the latter is twice that of the former. (octahedral NaCl crystal can be crystallized from the supersaturated solution of NaCl with urea. Absorption of Urea (111) on the NaCl (111) planes cause the growth rate of NaCl (111) rather slower than that of NaCl (100). (The 2D similarity of crystal structure cause such phenomena. Epitaxy Growth of Crystal When epitaxy growth, both gas and liquid, the match of lattice parameter should be considered. For example, in preparation of YBa2Cu3O7-d superconducting thin film, (a=3.88 Å, b=3.82 Å)，the substrate can be the single crystal slice: SrTiO3 (100), a=3.91 Å 。 In hydrothermal deposition of TiO2 thin film on Si(100), the lattice parameter of TiO2 : (a=5.354 Å, b=10.917 Å), d112=2asi,(a=5.43 Å, 2a=10.86 Å), so grow TiO2 thin film with high 112 orientation. Carbon shows both Layer and Cage Networks Carbon Allotropes Diamond Graphite Diamond sp3 hybrid C Td group One of the strongest/hardest material known High thermal conductivity (unlike ceramics) Transparent in the visible and infrared, with high index of refraction. Semiconductor (can be doped to make electronic devices) Metastable (transforms to carbon when heated) Sphalerite (ZnS) vs Diamond Structure Ball and stick shows us the 4-fold coordination in both structures Looking at tetrahedra in the structure helps us see the “diamond shape
Structures with the diamond framework reaction energy graphite(s)2 diamond (s) less dense more dense Diamond The diamond network with a single atom type The phase diagram The diamond network with alternate Zn &S 2atoms Reaction Energy vs Structure Pressure vs Structure reaction energy H2O(s 2 H2O( less dense more dense less dense more dense im chloride trueta reaction energy a-tin (s) z B-tin(s The transformation of (gray tin, diamond tetrahedral he rock salt to the structure stable below 13 c) accomplished at 298 K high P(10°atm Structures of Ionic Solids based on CCP Structures of ionic solid: Some Rules for Counting Atoms in a Unit Cell Ionic structures are prototypes for a wide range of solids entirely to that cell and counts as one atom Many of structures effectively described as close packed anions (occasionally cations)with 2. Face: An ion on a face is shared by two cells and nterstitial holes filled by cations(occasionally contributes y atom to the cell in question 3. Edge: An ion on an edge is shared by four cells and contributes 1 atom to the count 4. Corner. lon on a cornel cells and contributes 1/8 atom to the count
3 Structures with the Diamond Framework Diamond The diamond network with a single atom type Zinc Blende (ZnS) The diamond network with alternate Zn & S atoms The phase diagram for diamond and graphite (from J. Geophys. Res. 1980, 85, B12, 6930.) Reaction Energy vs Structure (gray tin, diamond structure, stable below 13oC) tetrahedral white tin Pressure vs Structure pressure + P - P The transformation of sodium chloride from the rock salt to the cesium chloride structure can be accomplished at 298 K at high P (~105 atm). pressure Structures of Ionic Solids Ionic structures are prototypes for a wide range of solids: Many of structures effectively described as close packed anions (occasionally cations) with interstitial holes filled by cations (occasionally anions). Some Rules for Counting Atoms in a Unit Cell 1.Body: An ion in the body of a cell belongs entirely to that cell and counts as one atom 2.Face: An ion on a face is shared by two cells and contributes ½ atom to the cell in question 3.Edge: An ion on an edge is shared by four cells and contributes ¼ atom to the count 4.Corner: An ion on a corner is shared by eight cells and contributes 1/8 atom to the count Structures of Ionic Solids based on CCP
Structures of lonic solids Structures of ionic solids Polyhedral Representations Some variations achieved by different filling of interstitial holes Defining the coordination environment of an ion as a 风回◆ 鄒灬 OCTAHEDRON l。T Structures of Ionic solids based on CCP Type and The rock salt structure Interstitial Hole Filling Hnlfoctahedral (Alternate 跚 Octahedral hole Rock salt structure in FCc structure Sodium chloride structure Structures of lonic solids based on ccp Cou Na+=6x+8x1/8 4 ions in cell C上=1+12x% 4 ions in cell NaF, NaBr, Nal Lix Kx, Rbx AgF, AgCl, AgBr, Mgo CaO, SrO, BaO, MnO, Coo, NiO, Cdo, NaH Mgs, Cas, SrS. BaS (=halides)
4 Polyhedral Representations Defining the coordination environment of an ion as a polyhedron Structures of Ionic Solids Polyhedral representations of structures by linking coordination polyhedra together Some variations achieved by different filling of interstitial holes Structures of Ionic Solids Formula Type and fraction of sites occupied CCP HCP All octahedral NaCl Rock Salt NiAs Nickel Arsenide AB Half tetrahedral (T+ or T-) ZnS Sphalerite ZnS Wurtzite AB2 All tetrahedral Na2O Anti-Fluorite CaF2 Fluorite not known AB3 All octahedral & tetrahedral Li3Bi not known Half octahedral (Alternate layers full/empty) A2B CdCl2 CdI2 Half octahedral (Ordered framework arrangement) TiO2 (Anatase) CaCl2 TiO2 (Rutile) A3B Third octahedral Alternate layers 2/3 full/empty YCl3 BiI3 Locations of Octahedral Holes in FCC Structure The Rock Salt Structure Rock Salt Structure Interstitial Hole Filling Structures of Ionic Solids based on CCP FCC Sodium Chloride Structure NaF, NaBr, NaI, LiX, KX, RbX, AgF, AgCl, AgBr, MgO, CaO, SrO, BaO, MnO, CoO, NiO, CdO, NaH, MgS, CaS, SrS, BaS (X=halides) Na+ = 6 x ½+ 8 x 1/8 = 4 ions in cell Cl- = 1 + 12 x ¼ = 4 ions in cell 1 ½ ½ ½ ½ ½ ½ 1/8 1/8 1/8 1/8 1/8 1/8 1/8 1/8 ¼ ¼ ¼ ¼ ¼ ¼ ¼ ¼ ¼ ¼ ¼ ¼ Structures of Ionic Solids based on CCP Counting Atoms
Structures of Ionic solids based on ccp Rock Salt(NaCD Structure Nearest(N and Next. Nearest (NN Neighbors 樂怒 NaCl CCP. O sites: 100% Motif: Cl at(0,0,0); Cs at (/z"z, 1p cScL CsCl Structures of ionic solids based on ccp Coordination:8-8(cubic) Adoption by chlorides, bromides and iodides of larger cations The Rock Salt Structure e.g. Cs*, TI. NH+ Coordination numl CN of each type of ion is 6 Cation cn Anion cn Structures of Ionic Solids based on CCP Structures of Ionic Solids based on CCP Fluorite structure CaF. /(Na,O Anti Fluorite) Rock Salt Structure-Summary oCCP CI with Nat in all Octahedral holes LAttice: FCC oMotif Clat(0.0.0): Na at(1.0.0 04Nacl in ur CCP Cas with F- in all Tetrahedral holes o Coordination: 6: 6(octahedraL) Motif. Ca=at(0,0,0); 2F-at(,. y,)&eg ye v2 OCation and anion sites are topologically HCaF, in unit cel identical In the netted Anti F ite s rudtutrt rc Anion positions are reversed
5 Nearest (N) and Next-Nearest (NN) Neighbors C N N N N N N NN NN NN NN NN NN NN NN NN NN NN NN Structures of Ionic Solids based on CCP Rock Salt (NaCl) Structure NaCl; CCP, O sites: 100% •Motif: Cl at (0,0,0); Cs at (1 / 2 , 1 / 2 , 1 / 2 ) •1CsCl in unit cell •Coordination: 8:8 (cubic) •Adoption by chlorides, bromides and iodides of larger cations, •e.g. Cs+ , Tl+ , NH4 + CsCl The Rock Salt Structure Coordination Numbers CN of each type of ion is 6 (6,6) coordination Cation CN Anion CN Structures of Ionic Solids based on CCP Rock Salt Structure ¾ Summary CCP Cl- with Na+ in all Octahedral holes Lattice: FCC Motif: Cl at (0,0,0); Na at (1/2 ,0,0) 4NaCl in unit cell Coordination: 6:6 (octahedral) Cation and anion sites are topologically identical Structures of Ionic Solids based on CCP CCP Ca 2+ with Fin all Tetrahedral holes Lattice: FCC Motif: Ca2+ at (0,0,0); 2F- at (1 / 4 , 1 / 4 , 1 / 4 ) & (3 / 4 , 3 / 4 , 3 / 4 ) 4CaF2 in unit cell Coordination: Ca 2+ 8 (cubic) : F- 4 (tetrahedral) In the related Anti-Fluorite structure Cation and Anion positions are reversed Structures of Ionic Solids based on CCP Fluorite structure CaF2 / {Na2O Anti-Fluorite}
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)
NiAs (Nickel Arsenide) Nickel Arsenide(NiAs) Structure An alternative unit cell origin is at As (rather than Ni) LAttice Constant: a=.602A. c=5.009A sHCP As with Ni in all Octahedral holes The coordination of Ni and As is 6, but their structures =b,c=8/3 Motf2Niat(0,0.0)&(0,0,2 /ne hep of As, and As exist in the trigonal prism of n os 2Asat(14)&Q2234) share face. The distance of Ni-Ni is only 2.50 A, close to 2NiAs in unit cell hat in metallie Ni, thus NiAs crystal shows obvious metalli cOordination: Ni 6(octahedral: As 6(trigonal en the cdirection. the NrN Structures of lonic Solids based on hcp also 6 bu HCP I with Cd in Octahedral holes of alternate tThe niAs structure is a com structure in metallic compounds CdI o oe made from (a) transition metals with 11u -block elements such a lodide As Sb. Bi. S. Se ooe mOtif Cd at(0.0.0) lCdI in unit ce cOordination: Cd-6(Octahedral) I-3(base pyramid) Structures of lonic Solids Based on HCP Structures of lonic solids based on hcp Cal, Cdl, Cadmium lodide Polyhedral representation is most useful using Cdl lodide ctahedra (compare with NiAs) Cdl NIAs Comparison ACBACB Cd(OH): Mnlg, Mn(OH), Fe(OH): CoBr. TiS, ZrS, Sns. HCPI with Cd in octahedral holes of alternate lavers TiTe, Ni(OHda
9 An alternative unit cell origin is at As (rather than Ni) NiAs (Nickel Arsenide) HCP As with Ni in all Octahedral holes Lattice: Hexagonal - P a = b, c =8/3a 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 (trigonal prismatic) vLattice Constant: a=3.602 Å, c=5.009 Å vThe coordination of Ni and As is 6，but their structures are different：Ni fill in the octahedronal coordination from the hcp of As, and As exist in the trigonal prism of Ni. vIn NiAs structure, the neighboring octahedra of Ni atoms share face. The distance of Ni-Ni is only 2.50 Å，close to that in metallic Ni, thus NiAs crystal shows obvious metallic. Nickel Arsenide (NiAs) Structure In the c-direction, the Ni-Ni distance is rather short. Overlap of 3d orbital gives rise to metallic bonding. The NiAs structure is a common structure in metallic compounds made from (a) transition metals with (b) heavy p-block elements such as As, Sb, Bi, S, Se. Coordination of As is also 6 but as a trigonal prism: CdI2 Cadmium Iodide Structures of Ionic Solids Based on HCP HCP I with Cd in Octahedral holes of alternate layers Lattice: Hexagonal - P Motif: Cd at (0,0,0); 2I at (2 / 3 , 1 / 3 , 1 / 4 ) & (1 / 3 , 2 / 3 , 3 / 4 ) 1CdI2 in unit cell Coordination: Cd - 6 (Octahedral) : I - 3 (base pyramid) CdI2 Cadmium Iodide Structures of Ionic Solids Based on HCP HCP I with Cd in Octahedral holes of alternate layers A c B A c B… … Polyhedral representation is most useful using CdI6 octahedra (compare with NiAs) CdI2 Cadmium Iodide Structures of Ionic Solids Based on HCP CdI2 structure: CaI2 ,Ca(OH)2 , MgBr2 ,MgI2 , Mg(OH)2 , Cd(OH)2 , MnI2 , Mn(OH)2 , Fe(OH)2 , CoBr2 ,TiS2 , ZrS2 , SnS2 , TiTe2 , Ni(OH)2
Structures of lonic solids based on hcp Rutile(Tio2) Structure Rutile structure CHCP anion lattice Octahedral holes occupi Ti for octahedral coordination s6.3)Coordination ETiO,-octahedra SOTi3-trigonalplanar 802 ions are in HCP aTiOs are in cornersharing along a and b directions; in edge sharing along c direction Rutile: ceramic pigment(white color) aUnit cell dimensions: a=4.5937A; c=2.9587 A Rutile Crystal Structure Anatase TiO2 )Structure 0=0+000°9 %,(%u)(%+u)%,u=0.31 锯O2 ions are in CCp sTiO are all in edge ompounds with the same structures: GeO., SnO,, PbO 00③ cRystal system MnO2、MoO2、NbO2wO2 A Structures of lonic solid Spinel Structure Some other ionic solid structures named for the mineral MgAlyo- general formula AB,Oa FCC array of- ions A cations occupy 1/8 of T holes pecies occupying holes O. Characteristic of some d-block oxides Fe,Ok Co O Mn Oa
10 Structures of Ionic Solids Based on HCP Rutile Structure HCP anion lattice ¾ ½ Octahedral holes occupied Arises from the preference of Ti for octahedral coordination (6,3) Coordination TiO6 –octahedra OTi3 –trigonalplanar Rutile: ceramic pigment (white color) Rutile (TiO2 ) Structure O2- ions are in HCP. TiO6 are in corner-sharing along a and b directions; in edge-sharing along c direction Crystal system:tetragonal Unit cell dimensions: a=4.5937 Å; c=2.9587 Å Rutile Crystal Structure Ti4+：000，½ ½ ½ O2- : uu0, (1-u)(1-u)0, (½+u)(½-u) ½, (½-u)(½+u) ½, u=0.31 Compounds with the same structures: GeO2、SnO2、PbO2、 MnO2、MoO2、NbO2、WO2、 CoO2、MnF2 and MgF2 etc． Anatase (TiO2 ) Structure O2- ions are in CCP. TiO6 are all in edgesharing . Crystal system: tetragonal Unit cell dimensions a = 3.7845 Å c = 9.5143 Å Structures of Ionic Solids Some other ionic solid structures Spinel –¾ named for the mineral MgAl2O4 –¾ general formula AB2O4 FCC array of O2- ions •A cations occupy 1/8 of T holes •B cations occupy ½ of O holes •Sometimes denoted A[B2 ]O4 •Square brackets indicate species occupying O holes •Characteristic of some d-block oxides •Fe3O4 , Co3O4 , Mn3O4 Spinel Structure
