| Phase | Crystal structure | Density (g/cm3) |
|---|---|---|
| alpha (α) | simple monoclinic | 19.86 |
| beta (β) | body-centered monoclinic | 17.70 |
| gamma (γ) | face-centered orthorhombic | 17.14 |
| delta (δ) | face-centered cubic | 15.92 |
| delta prime (δ′) | body-centered tetragonal | 16.00 |
| epsilon (ε) | body-centered cubic | 16.51 |
Plutonium occurs in a variety of allotropes, even at ambient pressure. These allotropes differ widely in crystal structure and density; the α and δ allotropes differ in density by more than 25% at constant pressure.
- ^ Baker, Richard D.; Hecker, Siegfried S.; Harbur, Delbert R. (Winter–Spring 1983). "Plutonium: A Wartime Nightmare but a Metallurgist's Dream" (PDF). Los Alamos Science. Los Alamos National Laboratory: 148, 150–151.