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Inorganic Structural Chemistry > Hole filling > Flashcards

Hole filling Flashcards

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1
Q

How many tetrahedral holes are there per sphere in hcp, and where are it/they located?

A

Two per sphere. One right above and one right below each sphere in the layer.

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2
Q

How many tetrahedral holes per sphere in hcp can be occupied?

A

One per sphere.

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3
Q

How many tetrahedral holes are there per sphere in ccp, and where are it/they located?

A

Two per sphere. One right above and one right below each sphere in the layer.

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4
Q

How many tetrahedral holes per sphere in ccp can be occupied?

A

All.

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5
Q

What kind of closest packing do we have in CaF2, and which holes are occupied?

A

In CaF2 we have cubic closest packing of Ca with all tetrahedral holes filled by F.

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6
Q

What kind of closest packing do we have in zinc blende, and which holes are occupied?

A

In zinc blende (e.g. sphalerite, ZnS), we have cubic closest packing of S with half tetrahedral holes filled by Zn.

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7
Q

What kind of closest packing do we have in wurtzite, and which holes are occupied?

A

In wurtzite (e.g. ZnS) we have hexagonal closest packing of S with half tetrahedral holes filled by Zn.

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8
Q

What is the difference between wurtzite and zinc blende?

A

Wurtzite is hcp and zinc blende in ccp. Both have ZnS with half tetrahedral holes filled.

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9
Q

What kind of closest packing do we have in rock salt (NaCl) and which holes are occupied?

A

In rock salt we have cubic closest packing of Na/Cl, with all octahedral holes filled by Cl/Na.

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10
Q

What kind of closest packing do we have in NiAs and which holes are occupied?

A

In NiAs we have hexagonal closest packing of As with all octahedral holes filled by Ni. Ni stacked on top of each other

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11
Q

What is the coordination polyhedra for As in NiAs-type structure?

A

Trigonal prism.

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12
Q

What is the coordination polyhedra for Ni in NiAs-type structure?

A

Octahedron.

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13
Q

What are Heusler alloys?

A

Heusler alloys are compounds with formula XYZ (Half-Heusler) or X2YZ (Full-Heusler). X and Y are transition metals, Z is p-block.

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14
Q

How can a Heusler alloy be described?

A

X2YZ (full Heusler), XYZ (half Heusler).

Two fcc-lattices superimposed (shifted [1/2 0 0]) occupied by X. For half Heuslers one of these is unoccupied.

All tetrahedral holes filled by alternating Y and Z.

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15
Q

What are Laves phases?

A

Compositions MM’2 where M are bigger than M’.

These can be regarded as a superstructure of CsCl. In these cases they have tetrahedra of M’ instead of a single atom. E.g. MgCu2.

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16
Q

How can the partial filling of CA2-compounds be in hcp?

A

Two types: CdI2 or CaCl2.

CdI2: Every second plane have fully filled octahedral holes.

CaCl2: Every plane has half filled octahedral holes.

17
Q

How can be the partial filling of CA2-compounds be in ccp?

A

One type: CdCl2

Every second plane have fully filled octahedral holes.

18
Q

How can the partial filling of CA3-compounds be in hcp?

A

Three types: Cr2AlC, RuBr3, BiI3

Cr2AlC: Every third plane fully filled octahedral holes.

RuBr3: Every plane filled 1/3 octahedral holes.

BiI3: Every second plane filled 2/3 octahedral holes.

19
Q

How can the partial filling of CA3-compounds be in ccp?

A

One type: YCl3

Every second plane filled 2/3 octahedral holes.

20
Q

How can the partial filling of C2A3-compounds be in hcp?

A

One type: Al2O3 (corundum)

Every plane filled 2/3.

21
Q

How can the partial filling of C2A3-compounds be in ccp?

A

One type: La2O3

Two planes filled fully octahedral holes, one plane empty.

22
Q

How is the packing in a spinel?

A

Spinel: AM2X4
In a spinel there is a combined fractional hole filling of tetrahedral and octahedral intersticies.

There is a cubic closest packing of X (usually oxygen). Two-thirds of metal ions occupy octahedral sites, the rest tetrahedral.

23
Q

What is an inverse spinel?

A

Spinel: AM2X4

Normally, larger ions will occupy octahedral sites and smaller ions with occupy tetrahedral sites.

In an inverse spinel, half of the M-ions occupy tetrahedral sites and half octahedral sites, while A occupy octahedral sites.

Degree of inversion is designated by λ (0 < λ < 0.5), where 0.5 indicates inverse spinel and 0 indicates normal.

24
Q

How can the closest packing in a perovskite be described?

A

ABX3 - cubic closest packing of AX.

25
Q

In hcp, how are the octahedral intersticies linked?

A
  1. Face-sharing when octahedra are located one on top of the other in the direction c.
  2. Edge-sharing when they are adjacent in the a-b plane.
  3. Vertex-sharing when they are adjacent at different heights.
26
Q

What are the bond angles between bridging atoms of the the octahedral intersticies in hcp for the different arrangements?

A
  1. Face-sharing: 70.5°
  2. Edge-sharing: 90°
  3. Vertex-sharing: 131.8°
27
Q

What are the bond angles between bridging atoms of the tetrahedral itnersticies in hcp for the different arrangements?

A
  1. Face-sharing: 56.7°
  2. Edge-sharing: 70.5°
  3. Vertex-sharing: 109.5°
28
Q

What are the bond angles between bridging atoms of the the octahedral intersticies in ccp for the different arrangements?

A
  1. Face-sharing: There are no face-sharing octahedra in ccp.
  2. Edge-sharing: 90°
  3. Vertex-sharing: 180°
29
Q

What are the bond angles between bridging atoms of the the tetrahedral intersticies in ccp for the different arrangements?

A
  1. Face-sharing: There are no face-sharing tetrahedra in ccp.
  2. Edge-sharing: 70.5°
  3. Vertex-sharing in octants with common edge: 109.5°
  4. Vertex-sharing in octants with common vertex: 180°
30
Q

How are MnP and NiAs related?

A

MnP is a distorted structure of the NiAs-type. Metal ions are closely linked in the ab-plane in a zigzag-pattern.

Inorganic Structural Chemistry (13 decks)

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