McCaw Chemistry

Resources written by Chas McCaw for sixth form chemistry teaching and beyond.

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Diamond 7: equivalence of the carbon atoms in the unit cell

A cube of eight unit cells is shown to the left. It is easier to appreciate with this view that the two colours of carbon atom in the structure (the grey face-centred cubic (FCC) carbons, and the blue carbons in the FCC tetrahedral holes) are in fact equivalent, and how a displacement of the unit cell along one of the carbon-carbon bonds will put the blue carbons in FCC sites. This is made even more explicit by rotating the cube horizontally by 45 degrees (ie around a central vertical axis), so that you can see along the hexagonal channels.

Go to page 8 to look at how the carbon backbone of cyclohexane can be seen within the diamond unit cell.

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