Diamond

Download the structure for interactive viewing

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Go to the Diamond FRAMEWORK at Stephen Heyes' website at Oxford University and click on the image of the diamond crystal structure to download and open in CrystalMaker for viewing, or...

Download the diamond structure as the .cmdf file called diamond structure ( 2kB Jun21 07) which you can import into CrystalMaker for viewing.

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Open the Crystal Structures Library on the CrystalMaker disc, and click on Minerals > Native Elements > Carbon-Diamond.

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Click on the DIAMOND file in the XtalDraw folder.

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Go to Crystal Structures (more info) and choose "Diamond lattice", which is listed under "Some common cubic lattices". This resource is currently off-line. Please check back at a later date.

Questions

1. What is the coordination number for each C atom?
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Four. The image below shows the local environment around a carbon in the diamond structure.

2. What is the shape of the polyhedron that forms if all of the nearest neighbor C atoms are connected?
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It is a tetrahedron (there are four apices equidistant from the center).

3. What type of bonds occur in diamond? What is the hardness of diamond? How is hardness related to bond type?
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The carbon atoms in diamond are bonded with covalent bonds. Covalent bonds are generally stronger than the other types of bonds (ionic, metallic, and Van der Waals), and contribute to the extremely high hardness of diamond (10 on the Mohs scale).
4. For CrystalMaker users, use the bond angle tool to determine the bond angle between any C atom and its two nearest neighbors.
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You should have obtained a bond angle of 109.47°.
5. Now let's explore the cleavage directions in diamond. The following instructions are for CrystalMaker users. First, expand the structure by clicking on Transform -> Set Range and clicking on "Expand" three times, followed by "Apply". Next, click on Transform -> Lattice Plane -> Edit and enter "1" in each of the boxes. (111) is a shorthand method of expressing the orientation of the resulting lattic plane in the mineral structure and the numbers are called "Miller indices". Move this plane as far away from C atoms as possible by using the lattic plane tool. Now note the distance between this plane and the surrounding C atoms. Next, draw a lattice plane for these Miller indices: (001) and move it with the lattic plane tool away from neighboring C atoms. Which plane, (111) or (001), will be more easily cleaved through diamond?
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   The (111) plane is weaker than (001) because the distances to neighboring C atoms is larger.
6. What is the relationship between bond angle and cleavage?