Crystal Structure of Delta-Prime Plutonium And the Thermal Expansion Characteristics Of Delta, Delta-Prime, and Epsilon Plutonium

Abstract

The σ′ plutonium is found to be body-centered-tetragonal with two atoms per unit cell at 000 and 1/2, 1/2, 1/2. The unit cell dimensions at 477°C are α = 3.339 ± 0.003Å and c = 4.446 ± 0.007Å, which lead to a calculated density of 16.01 g per eu cm. Each plutonium atom is surrounded by 12 others at a mean distance of 3.275Ă. The linear coefficient of thermal expansion perpendicular to the c-axis is 10⁶ ᾱ_a = 305 ±35 per °C, and parallel to the c-axis is 10⁶ ᾱ_c=−659 ± 67 per °C. The average linear coefficient, (2ᾱ_a + ᾱ_c)/3, is equal to 10⁶ᾱ_L = −18 ± 28 per °C. The linear coefficient of themal expansion of face-centered-cubic σ plutonium is found to be 10⁶ ᾱ_L=−8.6 ± 0.3 per °C, and of body-centered-cubic ∈ plutonium 10⁶ ᾱ_L = 36.5 ±1.1 per °C.