Solid Structures of Metals

Solid Structures of MetalsPreeti AghalayamBuilding up from basic unitsSodalite -> ZeoliteZeolite AZeolite YNotice how the placement and bonding between the basic sodalite cages can lead to different symmetries and properties(Vining & Auerbach, Personal Communication, 2010)Sodalite

Common catalyst structures

Do these pictures give you a clue?

fcc & hcpbccStructures of metal catalysts

HexagonalCatalyst propertiesDifferent metals tend to take different solid structures hcp, bcc, fcc are commonbcc: Ti, Cr, Fe, W, Mo, Vfcc: Ag, Au, Co, Cu, Ni, Pb, Pthcp: Be, Mg, Zn

Todays task is to understand something about the symmetry in each of these structures; & identify potential catalyst active sites.

Miller Indices(named for British mineralogist William Miller)Miller indicesMiller indices are a handy way of labelling the various possible intersecting surfacesThe Miller indices (hkl) refer to the (inverse of the) intercepts of the intersecting plane, on the three crystallographic axes:

(100)(110)(111)(210)(100), (110) & (111) are the common low-index planesLow index planes in bcc & fcc

SummaryLow index Miller planes for bcc & fcc were identifiedPotential adsorption sites on each type of plane were examinedProperties can be expected to be different at each of these sites, as surroundings are so differentTilted closely packed layer of fcc was identified as the fcc(111) planeAssignment (due Sunday 26th Aug) was announced

[bcc(100)][bcc(110)][bcc(111)]

[fcc(100)] [fcc(110)][fcc(111)]