Trap-state prediction in nanocomposite interfaces published in J. Mater. Research

PolyethyleneSilica

A. Shandilya, L. S. Schadler and R. Sundararaman, “First-principles identification of localized trap states in polymer nanocomposite interfaces”, J. Mater. Research, accepted (2020)

Polymer nano-composite materials have the potential to exhibit higher dielectric breakdown strength than pure polymers, primarily because of trap states introduced at the interfaces between the inorganic fillers and the polymer matrix. This work systematically identifies localized trap states in such polymer nano-composite materials. We create an ensemble of amorphous interfaces by combining polymer chains and glassy filler surfaces created by self-avoiding random walks and simulated quenching respectively. We introduce a parameter to quantify the extent of localization of every Kohn-Sham orbital using the inverse of its second spatial moment. After relaxing the polymer nano-composites using DFT, we used the localization parameter to identify most prominent states which can trap either electrons or holes. We find that these states correspond with distorted polyhedra and broken bonds, and significantly reduce in number and depth when dangling bonds are hydrogen-terminated. The distribution in space and energy of traps thus predicted will help select appropriate combinations of inorganic filler, surface functionalization and polymer matrix for the next generation of nano-dielectrics.