Module 2.2 - Crystal Structures Flashcards

1
Q

What is radius ratio?

A

The radius of the cation to the anion

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2
Q

What is the aim of the radius ratio?

A

To obtain the lowest amount of energy by maximizing attraction while minimizing repulsion.

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3
Q

If anions are too close to other anions in terms of the radius ratio, what happens to the structure?

A

They become unstable

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3
Q

If anions are too close to other anions in terms of the radius ratio, what happens to the structure?

A

They become unstable

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4
Q

How come for ZnS structures, tetrahedral coordination is still maintained even if the radius ratio is >0.414, which is supposedly octahedral?

A

Zinc Sulfide does this because it has 2 polymorphs, wurtzite (HCP), zinc blended (FCC - interpenetrating)

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5
Q

When usually is the tetrahedral coordination followed even if the radius ratio >0.414?

A

When atoms favor the sp3 hybridization, for small ∆EN.

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6
Q

How can the crystal structures of

A
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