Solid State Theory
Solid State Theory
Solid State Theory
Set of flashcards Details
Flashcards | 7 |
---|---|
Language | Deutsch |
Category | Physics |
Level | University |
Created / Updated | 23.02.2016 / 24.02.2016 |
Licencing | Attribution (CC BY) (Philip Gautschi) |
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Which solids have simple one Atom Basis?
Noble Metals (Au, Ag, Hg, ...)
Alkali Metals (Li, Na, K, Rb, Cs, Fr)
Iron
Aluminium
Crystal structure =
lattice + basis
Definition of a Bravais lattice?
A(r) = A(r+T) with T = n1*a1 + n2*a2 + n3*a3 n1,2,3 are integer
- The vectors are NOT unique.
- There are 5 Bravais lattices in 2D and 14 in 3D
What is a primitive cell?
A primitive cell fills the whole space without holes or overlapping.
- Parallelogram/-epipid based on the Bravais vectors. (not unique)
- every other shape which fills the whole space without holes or overlapping.
- Wigner-Seitz cell (rectangular or hexagon)
All primitive cells have the same Volume and have one lattice point. (Proof it)
(There are also non primitive cells which may have higher symmetry, body centered cube bcc)
Honeycomb lattice
is no Bravais lattice.
Graphene has a honeycomb lattice (two hexagonal lattices )It can be discribed as a hexagonal lattice with a basis of 2 atoms.
Rotational symmetrie
There is not only Translational symmetrie but also rotational.
There are only 2, 3,4,6 fold rotation symmetries allowed (Proof it).
(5 is possible in quasi crystals)
There are which and how many Bravais lattices?
- oblique (least symmetry) phi != 90 |a1| != |a2|
- rectangular phi = 90 |a1| != |a2| ( reflection and 180 Rotation)
- square phi =90 |a1| = |a2| (90 Rotation)
- hexagonal phi =60 |a1| = |a2| (60 Rotations)
- centered rectangular rhombic