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I. Structural Aspects Structural Chemistry Associated with Vacancies: Sc 1 x S

Hand-Outs: 42. I. Structural Aspects Structural Chemistry Associated with Vacancies: Sc 1 x S. Sc 1.11 S  Sc 0.81 S. (S-poor). (S-rich). Sc 1.11 S = ScS 0.9 (vacancies at S). Sc 1 x S (vacancies at Sc): S coordination is mixture of. Let u = fraction of 4-coord. S

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I. Structural Aspects Structural Chemistry Associated with Vacancies: Sc 1 x S

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  1. Hand-Outs: 42 I. Structural Aspects Structural Chemistry Associated with Vacancies: Sc1xS Sc1.11S  Sc0.81S (S-poor) (S-rich) Sc1.11S = ScS0.9 (vacancies at S) Sc1xS (vacancies at Sc): S coordination is mixture of Let u = fraction of 4-coord. S v = fraction of 6-coord. S u = 3x v = 1  3x ScS and

  2. Hand-Outs: 43 I. Structural Aspects Vacancies at Both Cation and Anion Sites: NbO “Chains” of Vacancies NaCl-type: Fm3m NbO-type: Pm3m Nb vacancies at corners O vacancies at center NbO: View down [111] (Body-diagonal) Coordination at Nb Coordination at O

  3. Hand-Outs: 43 I. Structural Aspects Vacancies at Both Cation and Anion Sites: NbO “Chains” of Vacancies NaCl-type: Fm3m NbO-type: Pm3m Nb vacancies at corners O vacancies at center NbO: View down [111] (Body-diagonal) d(Nb-O) = 210.5 pm d(Nb-Nb) = d(O-O) = 298 pm 2R(O2) = 280 pm 2R(Nb) = 286 pm Coordination at Nb Coordination at O

  4. Hand-Outs: 43 I. Structural Aspects Metal-Metal Bonding: Octahedral Clusters [M6X12]X6 [M6X8]X6 X(a) X(i) 14-16 valence electrons per M6 cluster for M-M bonding 20-24 valence electrons per M6 cluster for M-M bonding Nb6Cl14, Ta6Cl15, Zr6Cl12Z (Z = C, Fe) PbMo6S8, Nb6I11, Nb6I11H

  5. Hand-Outs: 43 I. Structural Aspects Metal-Metal Bonding: Octahedral Clusters [M6X12]X6 [M6X8]X6 X(a) X(i) H Z 14-16 valence electrons per M6 cluster for M-M bonding 20-24 valence electrons per M6 cluster for M-M bonding Nb6Cl14, Ta6Cl15, Zr6Cl12Z (Z = C, Fe) PbMo6S8, Nb6I11, Nb6I11H

  6. Hand-Outs: 44 I. Structural Aspects Metal-Metal Bonding: Layered Compounds 3.90 Å 3.32 Å 3.64 Å 2.89 Å 3.47 Å ZrTe2 (Zr4+; “d0”)  BaC BaC  NbTe2 (Nb4+; “d1”) MoTe2 (Mo4+; “d2”)

  7. Hand-Outs: 44 I. Structural Aspects Trigonal Prismatic Coordination; Metal-Metal Bonding MoS2 (“d2”)  BcB CaC  NbS2 (“d1”) “Charge Density Wave” (CDW) LiMoS2 (“d3”) Octahedral “Intercalation” Mo Li d(Mo-Mo) < 3.00 Å

  8. Hand-Outs: 45 I. Structural Aspects Octahedral vs. Trigonal Prismatic Coordination NaCl (Fm3m): CaS, ScP, TiC  AcBaCbAcBaCb  M: Octahedral; X: Octahedral WC (P-6m2): ZrS, WC  AbAb  M: Trigonal Prism. X: Trigonal Prism TiP (P63/mmc): TiP, HfAs  AcBcAbCb  M: Octahedral; X: ½ Oct., ½ T.P. NiAs (P63/mmc): TiS, VS  AcBcAcBc  M: Octahedral; X: Trigonal Prismatic

  9. Hand-Outs: 46 I. Structural Aspects Polymorphism in Layered Compounds: M3X8 and M3YX7 Nb3Cl8, Nb3Br8, Nb3I8: 3/4 Octahedral holes occupied in CP halide ions. Nb3YX7 (Y = S, Se, Te; X = Cl, Br, I): One CP sheet = (YX3); other = (X4) Y site is “pushed up” as M triangle forms “Ac(B)” M3 Triangle: 3 2-center, 2-electron M-M Bonds = 6 electrons for M-M Bonding. Nb3Cl8: (158) = 7 electrons (1 unpaired electron); Nb3SI7: (1527) = 6 electrons.

  10. Hand-Outs: 46 I. Structural Aspects Polymorphism in Layered Compounds: M3X8 and M3YX7 Nb3SBr7  Ac(B) Ac(B)  A = “Br4” Sheet (B) = “SBr3” Sheet Nb3TeI7  Ac(B) Ca(B)  A,C = “I4” Sheet (B) = “TeI3” Sheet Nb3TeBr7  Ac(B) (C)aB  A,B = “Br4” Sheet (B),(C) = “TeBr3” Sheet

  11. Hand-Outs: 47 I. Structural Aspects Polymorphism in Layered Compounds: Ta3TeCl7 and Ta3TeI7 AFM Peter Schmidt, Freiburg, GER Te pushed up by Ta3 Clusters Ta3TeI7 [TeI3] Sheet Ta3TeCl7 [I4] Sheet (Not Observed)

  12. Hand-Outs: 48 I. Structural Aspects Metal Dichalcogenides (MX2): Metal-Metal vs. Anion-Anion Bonding Rutile Chains of Edge-Sharing MX6 Octahedra TiO2, HT-VO2, HT-NbO2 2.61 Å 3.18 Å VO2 LT-VO2, LT-NbO2, MoO2 Monoclinic

  13. Hand-Outs: 48 I. Structural Aspects Metal Dichalcogenides (MX2): Metal-Metal vs. Anion-Anion Bonding Rutile CdI2 Chains of Edge-Sharing MX6 Octahedra c/a = 1.6 TiS2, ZrSe2, ZrTe2 TiO2, HT-VO2, HT-NbO2 2.61 Å 3.18 Å VO2 c/a = 1.4 Rh1+xTe2, IrTe2, NiTe2 LT-VO2, LT-NbO2, MoO2 Monoclinic

  14. Hand-Outs: 48 I. Structural Aspects Metal Dichalcogenides (MX2): Metal-Metal vs. Anion-Anion Bonding Rutile CdI2 Pyrite Chains of Edge-Sharing MX6 Octahedra c/a = 1.6 TiS2, ZrSe2, ZrTe2 TiO2, HT-VO2, HT-NbO2 FeS2, CoS2, RuSe2, RhTe2, Ir1xTe2 2.61 Å 3.18 Å VO2 (X-X)2 2 X2 c/a = 1.4 Rh1+xTe2, IrTe2, NiTe2 LT-VO2, LT-NbO2, MoO2 Monoclinic

  15. Hand-Outs: 49 I. Structural Aspects Eutactic Octahedral + Tetrahedral Structures

  16. Hand-Outs: 49 I. Structural Aspects Eutactic Octahedral + Tetrahedral Structures Na3As: HCP (P63/mmc) Li3Bi: CCP (Fm3m) a = 5.088 Å, c = 8.982 Å c/a = 1.765 As: Bi: 3.00 Å

  17. Hand-Outs: 50 I. Structural Aspects Li3Bi: BCC Packing Li3Bi: Fm3m Bi: “A” (0,0,0), (½, ½, 0), (½, 0, ½), (0, ½, ½) LiOCT: “B” (½, ½, ½), (0, 0, ½), (0, ½, 0), (½, 0, 0) LiTET: “C” (¼, ¼, ¼), (¾, ¾, ¼), (¾, ¼, ¾), (¼, ¾, ¾) “D” (¾, ¾, ¾), (¼, ¼, ¾), (¼, ¾, ¼), (¾, ¼, ¼) BCC Packing: Set all atom sizes equal…

  18. Hand-Outs: 50 I. Structural Aspects Eutactic Octahedral + Tetrahedral Structures

  19. Hand-Outs: 50 I. Structural Aspects Eutactic Octahedral + Tetrahedral Structures NaTl “Zintl Phases” CsCl CuMgSb LiMgSb

  20. Hand-Outs: 51 I. Structural Aspects HCP: Trigonal Bipyramidal Voids (Coalescing 2 Tetrahedral Voids) HCP:  BC  B = (⅓,⅔,¼) C = (⅔,⅓,¾) Oct: “a” = (0,0,0) Tbp: (⅓,⅔,¾) and (⅔,⅓,¼) AlB2 Structure Planar “Honeycomb” Net; 63 Net

  21. Hand-Outs: 52 I. Structural Aspects AlB2 – Nets and Distortions B Net in MgB2 63 Net AlB2 (P6/mmm) Al Net in CaAl2 3636 Net “Kagomé Net” CaIn2 (P63/mmc) Al Net in CuAl2 32434 Net ZnO (P63mc)

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