A. Huzayyin

Density functional analysis of chemical impurities in dielectric polyethylene

The effect of various chemical impurities in polyethylene on the electronic structure, trap depths, electron density, interchain interaction, etc. has been studied through the use of density functional theory. Quantum mechanical description of chemical impurity states is provided. The estimated depth of deep traps introduced directly by impurities and shallow traps introduced indirectly by impurity induced local disorder are in agreement with experimental estimates in the literature.

Quantum mechanical studies of carbonyl impurities in dielectric polyethylene

The effect of carbonyl impurities on the solid state physics of polyethylene has been studied through the use of density functional theory. Impurity formation energy, local physical disorder, effect on polyethylene electronic structure, and enhancement of interchain interaction were determined. Estimates of deep traps introduced directly by carbonyl and shallow traps introduced indirectly by carbonyl induced local disorder are in agreement with experimental data and other computational studies.

Quantum mechanical study of charge injection at the interface of polyethylene and platinum

Charge injection at a polyethylene/platinum interface is studied through use of density functional theory (DFT). Various crystal orientations at the interface hetero-structure are considered. The computed minimum barriers for electrons and hole injection at an impurity free interface are 3.15 and 2.62 eV, respectively. The work demonstrates that chemical impurities play an important role in the injection process. Impurity states, such as those of carbonyl, can reduce the effective barriers to charge injection to about 1.0 eV.

Density functional theory analysis of the effect of iodine in polyethylene

The interaction between iodine and polyethylene has been studied through the use of density functional theory (DFT) with the purpose of explaining the physical basis behind the increase in the conductivity of polyethylene upon doping with iodine. The interaction between polyethylene and various In stable configurations is characterized in terms of binding energy, bond lengths, electron charge density, changes in electron charge density, and mixing of atomic orbitals, all of which are determined through DFT. Based on the energy of iodine impurity states introduced into the bandgap and the spatial features of the impurity state wavefunctions, a mechanism by which iodine increases the conductivity of polyethylene is proposed. The mechanism explains the experimentally observed increase in hole mobility and decrease of activation energy of polyethylene upon doping with iodine.

An overview of impurity states and the basis for hole mobility in polyethylene

This study concentrates on the energy states introduced into the band gap of polyethylene by chemical impurities and the resulting implications for hole mobility in PE. The thermal activation energies of polyethylene with iodine impurity, PE, and polypropylene can be predicted from the energy of iodine and carbonyl impurity states above the valence band maximum, and the effect of chemical impurities on hole mobility can be related to the presence of interchain hybridized impurity states. Study of the interface between Pt and PE suggests that the Fermi level of the Pt is near the center of the PE band gap, which implies a barrier to charge injection of few electron volts. However in the presence of chemical impurities, such as carbonyl, the barrier to electron or hole injection from the Pt electrode is reduced to values similar to the activation energy of about 1 eV. Although impurity states are traditionally regarded as localized in the vicinity of chemical impurities, hybridized states involving certain impurities, such as iodine and carbonyl, can cause extension of the electron wave function between polymer chains and thereby increase hole mobility significantly, which is otherwise limited by VBM states which are normally extended only along polymer chains.

Utilizing the nonlinearity of a magnetic core inductor as a source of variable reactive power compensation in electric power systems

This paper attempts to present a rough sketch of the idea of using the nonlinearity of a ferromagnetic core inductor as a source of variable reactive power compensation in a power system. The theory behind the idea is presented as well as a sample implementation of it.

Effect of Carbonyl Impurities on Polyethylene Band Structure Using Density Functional Theory

The effect of carbonyl groups on crystalline polyethylene has been studied through computation of the energy band diagram and density of states using density functional theory (DFT). Carbonyl impurity states reduce the effective band gap by about 2.35 eV.

Quantum capacitance of graphene in contact with metal

We report a versatile computation method to quantitatively determine the quantum capacitance of graphene when it is in contact with metal. Our results bridge the longstanding gap between the theoretically predicted and experimentally measured quantum capacitance of graphene. Contrary to popular assumptions, the presence of charged impurities or structural distortions of graphene are not the only sources of the asymmetric capacitance with respect to the polarity of the bias potential and the higher-than-expected capacitance at the Dirac point. They also originate from the field-induced electronic interactions between graphene and metal. We also provide an improved model representation of a metal–graphene junction.

Computational quantum mechanics-based study of conduction in iodine doped polyethylene

Interaction between iodine and polyethylene relevant to conduction has been studied through the use of density functional theory. The interaction between I2 and polyethylene was characterized on an atomic level, and the role of I2 in linking the polymer chains electronically was demonstrated. The viability of a previously proposed conduction process in iodine doped polyethylene was demonstrated using quantum mechanical parameters.

First-principles study of aluminum-polyethylene interfaces

The ideal interfaces of aluminum with different configurations of polyethylene were studied through first principles calculations based on density functional theory. The theoretical vacuum energy shift caused by interfacial dipole moments agrees well with experimental result for Al-tetratetracontane (TTC, n-CH3(CH2)42CH3) interface. Although the interfacial dipole moments are considered, the calculated charge injection barriers are still higher than the experimental barriers. The reason is likely that chemical defects exist at the interface but are not included in this work.