Experiment 1
Exploring Crystal Structures
Visualize and compare the unit cells of SC, BCC, FCC, NaCl, and Diamond structures in 3D.
Controls
Key Equations
A crystal structure = Bravais lattice + basis. The unit cell is the smallest repeating volume.
APF = (n * 4/3 * π * r³) / a³
CN = Nearest neighbors
For close-packed structures: SC (n=1, APF 0.524), BCC (n=2, APF 0.680), FCC (n=4, APF 0.740).
Crystal Lattice Viewer
Atoms/Cell
1
CN
6
APF
0.524
Example
Polonium (Po)
Drag to rotate • Scroll to zoom
The simplest structure where atoms are located only at the corners of the cube.
Task: Compare Structures
Select each structure and record the properties in your table. Pay attention to the colors:
- Blue: Corner/A-type atoms
- Orange: Additional basis atoms
Teaching Connection
Crystal models are the first "abstract concept" students encounter. This 3D simulation is far more powerful than 2D diagrams. Consider: how would you adapt this to explain to Form 4 students why metals conduct electricity?
Reflection Questions
- Viewed along the body diagonal (⟨111⟩ direction), what shape do the face-centre atoms form in the FCC structure?
- Why is diamond extremely hard despite having such a low APF (0.340)? What type of bonding does diamond have?
- A metal crystallises in FCC with a = 3.61 Å. Identify the metal if its density is 8960 kg/m³.