The crystal structures of cerium metal at high pressure

The high-pressure form of cerium metal stable above 51 kbar, α'-Ce, is found to be orthorhombic with the α-uranium type of structure. At 58 kbar the cell dimensions of α'-Ce are a = 3.049, b = 5.998, c = 5.215 A. A second, metastable, phase of cerium metal, α”-Ce, has also been observed. It is monoclinic body-centered with a deformed cubic face-centered structure. The cell dimensions of α”-Ce at 56 kbar are a = 4.762, b = 3.170, c = 3.169 A, flβ = 91.73°. The volume change at the a-α' transition point is ΔV/V = 0.011. Cerium metal is fully tetravalent in both α'-Ce and α”-Ce.