$1Simplecrystal structuresTo form one ormore crystalline phases,where the atoms, molecules, or ions packtogetherHowthepropertiesofthesoliddependonthestructure
§1 Simple crystal structures To form one or more crystalline phases, where the atoms, molecules, or ions pack together How the properties of the solid depend on the structure
ClosepackingAatom was thought of as a hard sphereTwopossiblearrangementsfora layerofsuchidenticalatomsOnsqueezingthesquarelayerinfigure1 (a)the spheres would moveto the positions infigure 1 (b), so that the layer takes up lessspace
Close packing A atom was thought of as a hard sphere Two possible arrangements for a layer of such identical atoms On squeezing the square layer in figure 1 (a), the spheres would move to the positions in figure 1 (b), so that the layer takes up less space
(b)(a)Fig.1(a)asquarearrayof spheres(b) a close packed layer of spheres
(a) (b) Fig.1 (a) a square array of spheres (b) a close packed layer of spheres
Simple crystal structures-cubic closepacked3 LayersClosepackingstructures:ABA Hexagonal Close-Packing (HCP)Cubic vs.HexagonalABC CubicClose-Packing(CCP)packingefficiency74%
Close packing structures: Cubic vs. Hexagonal Simple crystal structures-cubic close packed packing efficiency 74%
Close Packing of SpheresABAhcp(a)(a)Mg, Be, Sc, Ti...Hexagonal ClosePackingCBAccp/fcc(b)Cu, Ca, Sr, Ag, Au, ..(b)Cubic Close Packing
Close Packing of Spheres