Question

Explain with diagrams the ccp mode of packing in crystals.

Answer 1

The ccp (cubic close packing) arrangement is one of the most efficient types of packing found in crystals. It is also known as face-centred cubic (fcc) packing. It is found in metals like copper, silver, aluminum, and gold.

1. First Layer (A): Atoms are arranged in a 2D hexagonal pattern; each atom touches six others.
2. Second Layer (B): Atoms are placed in the depressions of the first layer, fitting into the gaps, just like in hcp.
3. Third Layer (C): Atoms are placed in a new set of depressions, not directly above A or B. This gives an ABCABCABC... stacking pattern.