Clathrates:

• Type I: A2B6X46, cages: small AX12 (dodecahedron) and large BX14 (hexagonal truncated trapezohedron), examples: Na₂K₆Si₄₆, CO₂ or CH₄ in water ice cage.
• Type II: A4B2X34, cages: small AX12 (dodecahedron) and large BX16 (5¹²6⁴), examples: Na₄K₂Si₃₄, O₂ or N₂ in water ice cage.

Relation to foams:

• Weaire-Phelan structure corresponds to Type I clathrate.
• Kelvin structure corresponds to hypothetical NaSi₆ clathrate which in fact does not exist because of high angle and steric strains.