Q.Name the parameters that characterise a unit cell.

Step 1 – Edge parameters.

A unit cell has three edges meeting at a corner; their lengths are $a$, $b$ and $c$.

Step 2 – Angle parameters.

The three angles between these edges are:

• $\alpha$ — angle between edges $b$ and $c$,
• $\beta$ — angle between edges $a$ and $c$,
• $\gamma$ — angle between edges $a$ and $b$.

Step 3 – Summary. …

State the six defining parameters of a unit cell: three edge lengths and the three angles between the edges, wi …

• Giving only the three edge lengths and omitting the three angles.
• Mismatching angles to edges (e.g. saying $\alpha$ is between $a$ and $b$ — it is between $b$ and $c$). …