the nobel prize in chemistry 2011
DESCRIPTION
The Nobel Prize in Chemistry 2011. Dan Shechtman Technion – Israel Institute of Technology, Haifa, Israel Prize motivation: "for the discovery of quasicrystals ". Matter. Liquid Crystal. Solid. Liquid. Gas. Plasma. Amorphous. Crystalline. 1984. QUASICRYSTALLINE. T. Stable liquid. - PowerPoint PPT PresentationTRANSCRIPT
The Nobel Prize in Chemistry 2011
Dan ShechtmanTechnion – Israel Institute of Technology, Haifa, IsraelPrize motivation: "for the discovery of quasicrystals"
Matter
Solid Liquid Gas PlasmaLiquid Crystal
AmorphousCrystalline
QUASICRYSTALLINE
1984
L+
TStable liquid
UnderCooled liquid
log t
Tm
TTT Diagram for liquid-to-solid transformation
Coarse grained crystals
Fine grained crystals
glass
Crystal AmorphousSiO2
Crystal
3D Periodic arrangement of atoms
Amorphous
Random arrangement of atoms
Long-range translational order
Short-range order
No Long-range order
Short-range order
Sharp diffraction pattern
Diffuse diffraction pattern
Sharp
Crystalline Amorphous
Diffuse
Diffraction Patterns
Electron Diffraction and symmetry
Beam : <100>
Beam : <111>
9/87 7 crystal Systems
Cubic
Defining Crystal system Conventional symm unit cell
4
1
3
1
1
1
none
Tetragonal
Orthorhombic
Hexagonal
Rhombohedral
Triclinic
Monoclinic
a=b=c, ===90
a=bc, ===90
abc, ===90
a=bc, == 90, =120
a=b=c, ==90
abc, ==90
abc,
Rotational Symmetries
Z180 120 90 72 60
2 3 4 5 6
45
8
Angles:
Fold:
Graphic symbols
Crsytallographic Restriction
5-fold symmetry or Pentagonal symmetry is not possible for Periodic Tilings
Symmetries higher than 6-fold also not possible
Only possible rotational symmetries for periodic tilings
2 3 4 5 6 7 8 9…
A crystal with 10-Fold symmetry???
Five-fold
Two-fold
Five-fold
Two-fold Three-foldThree-fold
Icosahedral Symmetry
Icosahedron
Regular Polygons: All sides equal all angles equal
How many regular polygons are possible?
3 4 5 6
There are infinitely many regular polygons
Triangle square pentagon hexagon…
3D: Regular Polyhedra or Platonic Solids
Cube
How many regular solids?
Tetrahedron
All faces regular congruent polygons, all corners identical.
There are 5 and only 5 Platonic or regular solids !
Icosahedron
Octahedron
Tetrahedron
Cube
Dodecahedron
What is the structure of Quasicrystal?
One Dimensional Quasicrystal
Fibbonacci Chain
Two-dimensional Quasicrystal
Penrose Pattern
Hexagons always tile periodically
Square can tile periodically or aperiodically.
Is there a tile or a set of tile that will tile only aperiodically?
Thank you
