Electronic transport in disordered n-alkanes: From fluid methane to amorphous polyethylene

Abstract

We use a fast Fourier transform block Lanczos diagonalization algorithm to study the electronic states of excess electrons in fluid alkanes ͑methane, ethane, and propane͒ and in a molecular model of amorphous polyethylene ͑PE͒ relevant to studies of space charge in insulating polymers. We obtain a new pseudopotential for electron-PE interactions by fitting to the electronic properties of fluid alkanes and use this to obtain new results for electron transport in amorphous PE. From our simulations, while the electronic states in fluid methane are extended throughout the whole sample, in amorphous PE there is a transition between localized and delocalized states slightly above the vacuum level ͑ϳϩ0.06 eV͒. The localized states in our amorphous PE model extend to Ϫ0.33 eV below this level. Using the Kubo-Greenwood equation we compute the zero-field electron mobility in pure amorphous PE to be Ϸ2ϫ10Ϫ3 cm 2 /V s. Our results highlight the importance of electron transport through extended states in amorphous regions to an understanding of electron transport in PE.

Computer simulations of localized small polarons in amorphous polyethylene

“…These states are found to be in good agreement with the experimental data. 4,5 We also have been able to locate the mobility edge ͑separating localized and extended states͒ in amorphous polyethylene at about the vacuum level. The localized states extend to about Ϫ0.3 eV.…”

“…The initial equilibrium configurations of amorphous polyethylene at room temperature were generated using the procedure described in Ref. 5. The electronic wavefunctions are represented on a grid of 32 3 or 46 3 points, depending on the system size.…”

“…where V j r (r) is a short-range repulsive pair potential 5 and V p is the electrostatic energy that accounts for the point chargeinduced-dipole polarization interaction:…”

On the nature of high field charge transport in reinforced silicone dielectrics: Experiment and simulation

“…For small degree of disorder, delocalized states may still exist above the localized states, and the energy separating them is known as the mobility edge 14 . There have been many efforts to calculate the mobility edge for dielectric polymers via ab initio methods and charge mobilities are calculated assuming band transport [18][19][20] . On the other hand, extensive investigations in organic semiconductors have revealed that the electron-phonon coupling in molecular solids is very strong and electron transport can lose coherence even in the extended states 21,22 .…”

Fundamental theories and basic principles of triboelectric effect: A review

“…Even in particle triboelectrification (e.g., in pharmaceutical manufacturing), electron transfer is important. According to the nonequilibrium analysis conducted by Kron, Cubero, and Lacks et al [40][41][42] an excess of electrons trapped in the more easily transferred (presumably higher-energy) state is the driving force for the particle triboelectric initiation, as shown in Fig. 3 [1,42].…”