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Seminar 2/29/2012 - Stephen Garofalini, Rutgers University: Molecular Simulations of Nanoscale Materials

Title: Molecular Simulations of Nanoscale Materials: Applications in Conversion Materials for Advanced Batteries and Nanoconfined Water and Proton Transport

Abstract: We have applied molecular dynamics simulations to study two important, but diverse, topics involving behavior in (a) a nanoscale metal fluoride, FeF2, used as a conversion material in advanced high capacity Li-ion batteries and (b) the behavior of nanoconfined water and water reactions on oxide surfaces. In the first, exposure of FeF2 to Li+ causes a conversion reaction that forms nanocrystals of LiF and Fe-metal, enabling access to the multiple valence states of the iron cation. While these resultant nanocrystals are observed in post-reaction HRTEM, the molecular mechanisms and the reaction pathways in conversion are not understood, especially the controversial role of intercalation versus conversion. To address this problem, we apply an adaptive variable charge potential to study this reaction, showing the mechanisms for the formation of nanoclusters of Fe0 and LiF and the role of intercalation. In the second case, a dissociative water potential that matches many properties of bulk water and dissociatively reacts with silica surfaces was developed and applied to simulations of nanoconfined water. Results show the enhanced thermal expansion of nanoconfined water similar to Scherer’s experimental data, providing an explanation for the enhanced expansion. The simulations also show appropriate dissociative chemisorption of the water molecules on the silica surface as well as the enhanced formation of hydronium ions at these surfaces, similar to ab-initio molecular dynamics simulations. In addition to the formation of surface silanol (SiOH) sites, where protons are strongly bound, the simulations also show the location of weakly binding proton adsorption sites on the silica surface that contribute to enhanced proton transport.

All seminars are held on Wednesdays from 12:00 noon-1:00 p.m. in the Bowen Hall Auditorium Room 222. A light lunch is provided at 11:30 a.m. in the Bowen Hall Atrium immediately prior to the seminar.

Location: Bowen Hall Auditorium

Date/Time: 02/29/12 at 12:00 pm - 02/29/12 at 1:00 pm

Category: PRISM/PCCM Seminar Series

Department: PRISM