Studies of Vibrational Properties in Ga Stabilized d-Pu by Extended X-ray Absorption Fine Structure

TL;DR

This study uses temperature-dependent EXAFS to analyze vibrational properties in Ga-stabilized delta-phase plutonium alloys, revealing Ga-Pu bonds are stronger than Pu-Pu bonds and providing new insights into lattice stabilization.

Contribution

First unambiguous determination of Ga-specific vibrational properties in PuGa alloys using EXAFS, highlighting the strength difference between Ga-Pu and Pu-Pu bonds.

Findings

Ga-Pu bonds are significantly stronger than Pu-Pu bonds.

Ga-specific correlated-Debye temperature is approximately 202.6 K.

Lattice stabilization mechanisms are influenced by bond strength differences.

Abstract

Temperature dependent extended x-ray absorption fine structure (EXAFS) spectra were measured for a 3.3 at% Ga stabilized Pu alloy over the range T= 20 - 300 K at both the Ga K-edge and the Pu L_III-edge. The temperature dependence of the pair-distance distribution widths, \sigma(T) was accurately modeled using a correlated-Debye model for the lattice vibrational properties, suggesting Debye-like behavior in this material. We obtain pair- specific correlated-Debye temperatures, \Theta_cD, of 110.7 +/- 1.7 K and 202.6 +/- 3.7 K, for the Pu-Pu and Ga-Pu pairs, respectively. These results represent the first unambiguous determination of Ga-specific vibrational properties in PuGa alloys, and indicate the Ga-Pu bonds are significantly stronger than the Pu-Pu bonds. This effect has important implications for lattice stabilization mechanisms in these alloys.