Crystal Lattices

This simulation shows how atoms pack into a repeating unit cell. Students choose between simple cubic, body-centred cubic, face-centred cubic, rock salt and diamond, then change atom size, spin, bonds and space-filling display. A toggle expands one cell into a 2 by 2 by 2 supercell. Readouts give atoms per cell, coordination number, packing efficiency and the number of atoms shown. It supports lessons on solids, metals, ionic crystals and why different arrangements fill space differently.

• Switch between Simple cubic, BCC and FCC and compare the Atoms per cell readout.
• Read the Packing efficiency for each lattice and say which uses space most efficiently.
• Turn on 2x2x2 supercell and see how the single bright cell repeats in all directions.
• Choose Rock salt (NaCl) and describe how the two kinds of ion alternate.
• Enable Space-filling and Show bonds in turn to see touching atoms versus connections.

1. 1Describe a crystal as a unit cell repeated in three dimensions.
2. 2Calculate atoms per unit cell by counting shared corner, edge and face atoms.
3. 3Compare coordination number and packing efficiency across cubic lattices.
4. 4Identify the structures of sodium chloride and diamond.

Questions teachers ask