title: Topological ordering in liquid UO2.
abstract: A molecular dynamics model of liquid UO2 that is in good agreement with recent high-energy x-ray diffraction data has been analyzed using the Bhatia-Thornton formalism. A pre-peak appears in the topological structure factor S NN(Q) at Q  =  1.85(1)Å(-1) which is not present in the more common, element specific Faber-Ziman partial structure factors. A radical Voronoi tessellation of the 3D molecular dynamics model shows the presence of a wide distribution of clusters, consistent with presence of highly mobile oxygen atoms. However, 4-fold Voronoi polyhedra (n 4) are found to dominate the structure and the majority of clusters can be described by the distribution n 3  ⩽  n 4  ⩾  n 5. It is argued that an open network of 4-fold Voronoi polyhedra could explain the origin of the pre-peak in S NN(Q) and the topological ordering observed in liquid UO2.
authors.affiliation: X-ray Science Division, Argonne National Laboratory, Argonne, IL 60439, USA.
authors.forename: C J
authors.initials: CJ
authors.lastname: Benmore
authors.forename: L B
authors.initials: LB
authors.lastname: Skinner
authors.forename: B
authors.initials: B
authors.lastname: Lee
authors.forename: J K R
authors.initials: JK
authors.lastname: Weber
authors.forename: J B
authors.initials: JB
authors.lastname: Parise
authors.forename: M
authors.initials: M
authors.lastname: Williamson