Equilibrium thermodynamics of radiation defect clusters in δ-phase Pu–Ga alloys

• Published in: Journal of nuclear materials 2016-01, Vol.468, p.46-55
• Main Authors: Karavaev, A.V., Dremov, V.V., Ionov, G.V.
• Format: Article
• Language: English
• Subjects: Alloys; Classical molecular dynamics; Clusters; Defects; Free energy; Lattice vacancies; Lattices; Molecular dynamics; Primary radiation defect clusters; Radioactive aging; Thermodynamic integration; Thermodynamics; δ-phase Pu–Ga alloys
• ISSN: 0022-3115; 1873-4820
• DOI: 10.1016/j.jnucmat.2015.11.015

The paper presents a theoretical investigation into the response of δ-phase Pu–Ga alloys to self-irradiation. Using classical molecular dynamics we investigate the long-term behavior of primary radiation defects (vacancies) in the face-centered cubic lattice of the alloys under ambient conditions. High diffusive migration energy barriers and the corresponding low mobility of vacancies do not allow us to track their dynamics in the lattice by direct molecular dynamics simulations. Instead, we use the Helmholtz free energy to investigate the equilibrium thermodynamics of metastable microconfigurations of Pu–Ga crystals with artificially introduced vacancy clusters in various regular and random configurations. The Helmholtz free energy of the microconfigurations are calculated with the thermodynamic integration method. Based on the free energy evaluation we draw conclusions about the relative thermodynamic stability of various microconfigurations under ambient conditions. The equilibrium parameters of vacancy clusters in the bulk of the lattice and in the presence of edge dislocations are estimated.