Coordination number in ideal spherical nanocrystals

The effect of very small crystal sizes on the average coordination number (ACN) was evaluated by computer calculations. For well ordered materials, the experimentally measured ACN is often very near the theoretical maximum, i.e. the infinite lattice limit. However, even in perfectly ordered crystals the coordination number has a significantly lowered value if the crystals are nanosized. For very small nanocrystals, the ACN drops down to 70-80% of the infinite lattice limit and such variation can be detected experimentally. A quick and accurate way of estimating the theoretical ACN from the first four coordination shells of simple cubic, face-centred cubic, body-centred cubic and hexagonal close-packed spherical nanocrystals is introduced.