Stan Zygmunt

Relativistic density functional investigation of Pu(H2O)n3+ clusters

The solvation of the Pu{sup 3+} ion in water was investigated using relativistic density functional theory including generalized gradient corrections. Binding energies and optimized geometries for different coordination numbers of water molecules [Pu(H{sub 2}O){sub n}{sup 3+}, n=6, 8, 9, 10, 12] around the ion were calculated. The results indicate that the first solvation shell of Pu{sup 3+} is likely to contain eight or possibly nine waters with a Pu-O bond length of 2.51-2.55 {angstrom}. The theoretical results are compared with two recent EXAFS experiments on the Pu{sup 3+} aqueous system.

Surface-dependence of Interfacial Binding Strength Between Zinc Oxide and Graphene

There is an increasing interest in hybrid materials with impacts such as improving structural integrity of known and commonly used materials. Recent experiments have suggested that the adhesion of zinc oxide (ZnO) nanowires with carbon fibers can significantly improve interfacial shear and tensile strength of fiber reinforced polymer composites. We have carried out a systematic study of the interaction between ZnO and graphene based on density functional theory, with a focus on the effect of the surface orientation and termination of ZnO. The interaction has been explored through varying both the orientation and binding sites of the interacting surfaces. The calculated binding strength shows a strong dependence on the surface orientation and termination of ZnO, which can be explained from the difference in electronegativity of Zn and O, and the induced charge redistribution owing to the in-plane and out-of-plane dipole moment of the oxide surface.