Enhancing the electrostatic interactionsAllpolarsurface4Xexposed甲甲甲④④④A4+④002④58050CZn2+++Moltensalt400nnNChem. Comm. 5572 (2005)
c {101} Enhancing the electrostatic interactions All polar surface exposed 极性面㊉(001) ㊉ ㊉ ㊉ ㊉ ㊉ Molten salt Chem. Comm. 5572 (2005)
Why do we need ZnO with polar surfaces exposed?piezoelectriceffectIonic crystals with polar surfaces exposed alwaysexhibit piezoelectric effect,a physical property thatcan be exploited to turn mechanical energy intoelectricity.C
piezoelectric effect Ionic crystals with polar surfaces exposed always exhibit piezoelectric effect, a physical property that can be exploited to turn mechanical energy into electricity. Why do we need ZnO with polar surfaces exposed?
Wurzite: New Solid phase of MnOMost transition metal:Mn-oxides (MO, M=Sc, ....Ni) have a cubicrocksalt crystal structure2.079A1.963ABut ZnO and CoO arethe only stabletransition110.55°metal oxides known to108.38°possess a hexagonalstructureRecently,thehexagonalstructure of MnO hasbeen synthesized by010]100[001Park, J. T. et alWurzite structure of MnOJ. Am. Chem. Soc. 2012. 134, 8392
Wurzite structure of MnO J. Am. Chem. Soc. 2012, 134, 8392 • Most transition metal oxides (MO, M= Sc, .Ni) have a cubic rocksalt crystal structure. • But ZnO and CoO are the only stable transition metal oxides known to possess a hexagonal structure. • Recently, the hexagonal structure of MnO has been synthesized by Park, J. T. et al. Wurzite: New Solid phase of MnO
NiAs (R+/R: 0.732-0.414)FesNormalpicturePacking of anions:hcp(Two anions within a primary cell!)Cations:AlloctahedralholeshPBravais Lattice:6:6C.N. ofA- & B+:Na:NB in a unit cell: 2:2Ni,As2Structural motif:Alternativepicture:Cations ～layered hexagonal structureAnions:triangular prism holes (1/2)Ni: 0, 0, 0;0, 0, 1/21/3, 2/3, 1/4;2/3, 1/3, 3/4;As:
• Cations: All octahedral holes • Bravais Lattice: hP • C.N. of A- & B+ : 6:6 • NA :NB in a unit cell: 2:2 • Structural motif: Ni2As2 NiAs (R+ /R- : 0.732-0.414) FeS Ni: 0, 0, 0; 0, 0, 1/2 As: 1/3, 2/3, 1/4; 2/3, 1/3, 3/4; Alternative picture: Cations ~ layered hexagonal structure Anions： triangular prism holes (1/2) • Packing of anions: hcp (Two anions within a primary cell!) Normal picture
CsCIcubic, C.N.+:C.N.- 8:8CubicCsBrCs(R./R: 1-0.732)Thepacking ofanions:CubicP·Bravais Lattice:The position ofCubic holescations:8:8The C.N. of cationand anion:1:1Atomnumberinone unit cell:A: 0,0,0B: 1/2,1/2,1/2Please think about the coordination-polyhedra representation forthis type of crystals! (co-edge or cofacial stack?)
CsCl cubic, C.N.+ :C.N.- 8:8 A: 0,0,0 B: 1/2,1/2,1/2 CsBr, CsI (R+ /R- : 1-0.732) • The packing of anions: Cubic •Bravais Lattice : Cubic P •The position of cations: Cubic holes The C.N. of cation and anion: 8:8 • Atom number in one unit cell: 1:1 Please think about the coordination-polyhedra representation for this type of crystals! (co-edge or cofacial stack?)