Alpha-plutonium's polycrystalline elastic moduli over its full temperature range.
alpha-plutonium's volume-corrected polycrystal elastic moduli were measured between 18 K and the upper limit of its occurrence, near 400 K. The two independent moduli for a polycrystal-bulk and shear-behave smoothly, indicating no phase transition. Both moduli show the same 50% increase on cooling, an order of magnitude larger than in other metals. The Debye temperature obtained from low-temperature elastic moduli, 207 K, significantly exceeds most previous estimates. The Gruneisen parameter gamma=5.3, obtained from the temperature dependence of the bulk modulus, is intermediate among previous estimates using other approaches, alpha-plutonium's Poisson ratio nu is low: 0.18, nearly temperature independent, and its small decrease on warming opposes usual behavior. The high gamma, large but equal bulk modulus and shear modulus fractional stiffening on cooling, and near-temperature-invariant nu are attributed to a single mechanism: 5-f electron localization-delocalization.
Migliori
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A
Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA. migliori@cybermesa.com
Pantea
C
C
Ledbetter
H
H
Stroe
I
I
Betts
J B
JB
Mitchell
J N
JN
Ramos
M
M
Freibert
F
F
Dooley
D
D
Harrington
S
S
Mielke
C H
CH