Understanding the radiation-induced amorphization of zirconolite using molecular dynamics and connectivity topology analysis

作者：Foxhall H R^*; Travis K P; Hobbs L W; Rich S C; Owens S L

来源：Philosophical Magazine, 2013, 93(4): 328-355.

DOI：10.1080/14786435.2012.718448

• amorphization
• zirconolite
• connectivity topology analysis
• molecular dynamics simulation

Connectivity topology analysis is a powerful method for describing both crystalline structures and their metamict or amorphous analogues, because it places no reliance on symmetry operators or periodic translation, which vanish upon introduction of disorder to a material. Topological analysis represents atomic systems as graphs, and analysis of closed circuit connectivity (rings) is used to search for shortest non-degenerable connectivity paths that define the structure. A connectivity topology analysis is presented of crystalline zirconolite, a potential actinide-accommodating nuclear waste material. Characteristic topological differences are established in the connectivities of radiation-damaged and melt-quenched zirconolite structures generated by molecular dynamics simulations. Amorphization induced by alpha-recoil displacement cascades still retains certain short- and intermediate-range ordered configurations, particularly for Ti atoms. [TiO x ] polyhedral edge-sharing chains are observed in the metamict state, which may act to stabilize the radiation-damaged structure and prevent recovery of the initial crystalline phase. An assessment of the predicted amorphizability of zirconolite, based on the topological constraints imposed by its structure, reveals that the varying structural rigidity of the layers in the zirconolite structure is crucial to its amorphizability behavior. The hexagonal tungsten bronze structure [TiO x ] layer in particular provides weak constraints that are responsible for zirconolite%26apos;s comparative ease of amorphization.

• 出版日期2013-2-1