Crystal chemical formulae Flashcards
How are the linkage type of the overall structure written for different types of structures?
3D linked structure: 3 over ∞
2D sheet structure: 2 over ∞
1D fibre structure: 1 over ∞
Finite molecule: []
How are shapes of molecules characterised in crystal chemical formulae?
^ for a chain structure of finite length
O for a cyclic structure
Ⓥ for a cage molecule
E.g.Ⓥ[P4] - white phosphorus
How are the linkage type of a partial structure written when a certain atom has a certain linkage with another atoms of the same type?
^ for a chain structure of finite length
O for a cyclic structure
Ⓥ for a cage molecule
Then the atoms in questions are placed in brackets.
E.g. Na4Ⓥ[Si4]
How are coordination notated in crystal chemical formulas?
In superscripted brackets after the unique atom. Number indicates how many atoms it is coordinated by, letter indicates what type of coordination (e.g. o = octahedral, t = tetrahedral, s = square planar)
E.g. CaTiO3
Ca[8,12;]Ti[8,6o;]O3[4,2;]
Which coordination polyhedron does the symbol 2l denote?
Two atoms collinear with A
Which coordination polyhedron does the symbol 2n denote?
Two atoms, non-collinear with A
Which coordination polyhedron does the symbol 3l denote?
Triangle, coplanar with A
Which coordination polyhedron does the symbol 3n denote?
Triangle, non-coplanar with A
Which coordination polyhedron does the symbol 4s denote?
Square, coplanar with A
Which coordination polyhedron does the symbol 4n denote?
Square, non-coplanar with A
Which coordination polyhedron does the symbol 4t denote?
Tetrahedron
Which coordination polyhedron does the symbol 4y denote?
Triangular pyramid with A at centre of base.
Which coordination polyhedron does the symbol 5l denote?
Pentagon
Which coordination polyhedron does the symbol 5y denote?
Tetragonal pyramid
Which coordination polyhedron does the symbol 5by denote?
Trigonal bipyramid
Which coordination polyhedron does the symbol 7by denote?
Pentagonal bipyramid
Which coordination polyhedron does the symbol 6o denote?
Octahedron (trigonal antiprism)
Which coordination polyhedron does the symbol 6p denote?
Trigonal prism
Which coordination polyhedron does the symbol 6p1c denote?
Monocapped trigonal prism
Which coordination polyhedron does the symbol 6p2c denote?
Bicapped trigonal prism
Which coordination polyhedron does the symbol 6p3c denote?
Tricapped trigonal prism
Which coordination polyhedron does the symbol 8cb denote?
Cube (tetragonal prism)
Which coordination polyhedron does the symbol 8ap denote?
Square antiprism (tetragonal antiprism)
Which coordination polyhedron does the symbol 8ap1c denote?
Monocapped square antiprism
Which coordination polyhedron does the symbol 8ap2c denote?
Bicapped square antiprism
Which coordination polyhedron does the symbol 8by denote?
Hexagonal bipyramid
Which coordination polyhedron does the symbol 12co denote?
Cuboctahedron
Which coordination polyhedron does the symbol 12aco denote?
Anticuboctahedron
Which coordination polyhedron does the symbol 12i denote?
Icosahedron
Which coordination polyhedron does the symbol 12p denote?
Hexagonal prism
Which coordination polyhedron does the symbol 14FK denote?
14-vertex Frank-Kasper polyhedron
Which coordination polyhedron does the symbol 15FK denote?
15-vertex Frank-Kasper polyhedron
Which coordination polyhedron does the symbol 16FK denote?
16-vertex Frank-Kasper polyhedron
What does the symbol t mean for polyhedra?
Tetrahedron
What does the symbol s mean for polyhedra?
Square
What does the symbol o mean for polyhedra?
Octahedron
What does the symbol cb mean for polyhedra?
Cube
What does the symbol do mean for polyhedra?
Dodecahedron with triangular faces
What does the symbol co mean for polyhedra?
Cuboctahedron
What does the symbol i mean for polyhedra?
Icosahedron
What does the symbol l mean for polyhedra?
Linear/planar
What does the symbol n mean for polyhedra?
Non-linear/non-planar
What does the symbol y mean for polyhedra?
Pyramidal
What does the symbol p mean for polyhedra?
Prismatic
What does the symbol a mean for polyhedra?
anti-
What does the symbol b mean for polyhedra?
bi-
What does the symbol c mean for polyhedra?
Capped. 1c = monocapped, 2c = bicapped, 3c = tricapped
How can non-bonding orbitals be described in crystal chemical formulae?
With heavy bar under the element symbol.
What is the Frank-Kasper method for deteremining coordination?
You create a Wigner-Seitz cell around the atom in question. This is done by drawing a line between all neighbouring atoms, and cutting it in half, and finding the smallest volume that encapsulates these half-way points.
All atoms emerging from the faces of this domain is part of the coordination polyhedron.
Which three balances must be met for crystal chemical formulae?
For compound: C_m ^c+[C] A_n ^a-[A]
- Electroneutrality: m * c = n * a
- Connectivity: m * C = n * A
- Bond valence: c/C = a/A
What is the gap method for determining coordination?
When plotting bond distances from A to neighbouring atoms as a histogram, there usually is a large gap after a cluster of bonds. The gap method counts all the bonds occuring before the gap as part of the coordination polyhedron.
