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Calcium carbide IV ?

Dear Reader,

I think that I might be losing count of the number of posts on calcium carbide but here are some of the pictures of the solid. One common form of the compound is the tetragonal form which can be thought of as being like a cube, except the cube has been compressed or stretched on one edge to make a less symmetric box. Here is a view of one unit cell, I have added a couple of carbon atoms in near by cells to show the anions in all their glory.

Tetragonal calcium carbide unit cell

Tetragonal calcium carbide unit cell

Now that is not the end of the story, other forms of calcium carbide exist. For example there is a cubic high temperature form. This solid has disordered anions, without disorder it would have an impossible formula of CaC8. Here is a picture of the unit cell for you to look at.

Cubic calcium carbide

Cubic calcium carbide

Now we are not going to stop here, there are at least two more solid state forms of calcium carbide. Here is the monoclinic form, how monoclinic does not mean a single place where a doctor, dentist or vet works. Instead is it a type of unit cell, in a monoclinic cell one of the angles is not a right angle. Now for your delight here is a picture of the cell.

You should be able to see that it has the anions and calciums, the anions and calciums form chains. Here are the calcium ions and the anions.

Monoclinic calcium carbide only the bonds in the carbide anions are shown

Monoclinic calcium carbide only the bonds in the carbide anions are shown

Now we add the bonds to show the chains in the solid.

Monoclinic calcium carbide with the metal carbon bonds which form the chains

Monoclinic calcium carbide with the metal carbon bonds which form the chains

Now we add the bonds which interlink the chains.

Monoclinic calcium carbide with some of the bonds which link the chains together.

Monoclinic calcium carbide with some of the bonds which link the chains together.

Some other views of the monoclinic compound will be shown soon.

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