Question

There are four vacant tetrahedral sites in a unit cell of dc structure can four additional carbon atoms occupy these sites ? Give reason

Answer 1

There are four vacant tetrahedral sites in a unit cell of dc structure can four additional carbon atoms occupy these sites ? Give reason

Explanation:

Due to the fact in diamond are  bound covalently ,  all the available electrons are already occupied in other bonds.

Every atom of carbon can form 4 bonds with other atoms in a tetrahedral arrangement through sharing an electron pair between them.

When this happens, the atoms  make very close approaches ; the Van der Waals atomic radius of carbon is 170 pm therefore without an extra bonding force one would expect carbon atoms to stack up at distances of 340 pm.

The bonding distance in a diamond of 154 pm is less than half of the stacking distance!.

If one looks at the vacant tetrahedral sites in diamond they  will see that there is no vacant space at all to fit anything. This is due to the wonderful nature of covalent bonding that the occupied tetrahedral sites contain carbon atoms in the first place.

Note: the density of diamond, which at 3.5 g/cm ³  is much higher than that of other compounds consisting of only light atoms.Therefore diamond is already quite full as it is