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    • Tailoring Drug Mobility by Photothermal Heating of Graphene Plasmons
    Authors: Anh D. Phan; Nguyen K. Ngan; Do T. Nga; Nam B. Le; Chu Viet Ha;  Advisor: -;  Co-Author: - (2022)

    A theoretical approach to quantitatively determine the photothermally driven enhancement of molecular mobility of graphene-indomethacin mixtures under infrared laser irradiation is proposed. Graphene plasmons absorb incident electromagnetic energy and dissipate them into heat. The absorbed energy depends on optical properties of graphene plasmons, which are sensitive to structural parameters, and concentration of plasmonic nanostructures. By using theoretical modelling, temperature gradients of the bulk drug with different concentrations of graphene plasmons are calculated. From these, the temperature dependence of structural molecular relaxation and diffusion of indomethacin are determined and how the heating process significantly enhances the drug mobility is found out.
    • Confinement Effects on the Spatially Inhomogeneous Dynamics in Metallic Glass Films
    Authors: Anh D. Phan;  Advisor: -;  Co-Author: - (2022)

    This work develops the elastically collective nonlinear Langevin equation theory to investigate, for the first time, the glassy dynamics in capped metallic glass thin films. Finite-size effects on the spatial gradient of structural relaxation time and glass transition temperature (Tg) are calculated at different temperatures and vitrification criteria. Molecular dynamics is significantly slowed down near rough solid surfaces, and the dynamics at location far from the interfaces is sped up. In thick films, the mobility gradient normalized by the bulk value obeys the double-exponential form since interference effects between two surfaces are weak. Reducing the film thickness induces a strong dynamic coupling between two surfaces and flattens the relaxation gradient. The normalized gra...
    • Theoretical insights into non-Arrhenius behaviors of thermal vacancies in anharmonic crystals
    Authors: Tran, Dinh Cuong; Anh D. Phan;  Advisor: -;  Co-Author: - (2022)

    Vacancies are prevalent point defects in crystals, but their thermal responses are elusive. Herein, we formulate a simple theoretical model to shed light on the vacancy evolution during heating. Vibrational excitations are thoroughly investigated via moment recurrence techniques in quantum statistical mechanics. On that basis, we carry out numerical analyses for Ag, Cu, and Ni with the Sutton–Chen many-body potential. Our results reveal that the well-known Arrhenius law is insufficient to describe the proliferation of vacancies. Specifically, anharmonic effects lead to a strong nonlinearity in the Gibbs energy of vacancy formation. Our physical picture is well supported by previous simulations and experiments.