Robert O’Brien

Advisor: Dr. Jeff Greathouse

SLU Festival of Science 2001 Poster Presentation

Molecular dynamics studies of aqueous anion interactions with
uranyl-quartz surface complexes

We used molecular dynamics calculations to investigate the interaction between the aqueous uranyl ion and a quartz (0 1 0) surface.  Radial distribution function (RDF) calculations from the equilibrium portion of the simulation show five solvating water molecules with a U–water O distance of 2.50 Å. Two hydroxide ions were introduced into the system in order to determine the effect of anions on uranyl solvation structure and to see any effects of a basic environment on the uranyl/quartz interactions.  The hydroxide ions replaced two water molecules that were previously located in the solvation shell, resulting in the UO₂(OH)₂(H₂O)₃ complex.  RDF data showed that these hydroxide ions were located at 2.33 Å from the uranium atom while the uranium-water oxygen distance increased to 2.55 Å.  The quartz surface was partially deprotonated in later simulations.  The resulting surface complex showed the uranyl ion resting parallel to the quartz with two surface oxygens replacing water molecules in the solvation shell.  Over the course of the simulation, the uranyl ion remained in a fixed complex with the surface oxygens.