First Principles Studies of Interface Dielectric Properties of Polymer/metal-oxide Nanocomposites}

摘要: This thesis is devoted to studying interface dielectric properties of polymer nanocomposites from first principles. We aim understand at atomic scale the role effects and finite size nanoparticles in determining effective nanocomposites. To study surface principles, we investigate two common methods, namely dipole correction Coulomb cutoff, used eliminate artificial introduced by using supercell approximation. implement cutoff technique a plane-wave-based density functional theory code compare it with for same system under conditions. By comparison, both methods are shown be equivalent able remove periodic images very accurately. also find that combination these offers an easy way distinguish localized bound states interest highly delocalized unoccupied while relatively small supercell, ascertain convergence results respect size. To scale, develop new nanoscale averaging model connect macroscopic quantities corresponding microscopic ones. allows us compute spatially resolved local permittivity, including critically important ionic contributions, interfaces other complex structures. In this model, simple evaluating real-space decay length nonlocal functions proposed. By our supercells, calculate optical static permittivity profiles (polypropylene) / metal-oxide (PbTiO$_3$ alumina) nanocomposites. Our {em ab-initio} show metal-oxide/polymer mostly confined side, slabs can on average retain value bulk permittivity. These findings suggest classical mixing laws associated composites applied overall constant real polymer/metal-oxide nanocomposite system.