Ab-initio modeling of interfacial region in nanocomposite dielectrics

The interfacial region between a base matrix and nanoparticles in nanocomposite dielectrics is often referred to as the main cause of good performance of nanocomposites as insulating materials. In the present work we compare electronic structure of the interfacial region in the polyethylene magnesium oxide nanocomposite with the electronic structures of its bulk constituents. The calculations were performed with density functional theory, the LDA and AM05 functionals were used. Hydroxylated, silanol-terminated (-SiOH) MgO surfaces and an interface (a surface with grafted through Si alkane chains) were studied. Investigation has shown the presence of surface states in untreated (hydroxylated) MgO (111) surface, while for both silanized surfaces these states are removed. It results in 1.7 eV higher band gap energy compared to the untreated case. Untreated regions present in treated nanoparticle are proposed to behave as traps for electrons.