Computer simulations of localized small polarons in amorphous polyethylene

Cubero, David; Quirke, N.

doi:10.1063/1.1667471

Cited by 35 publications

(30 citation statements)

References 14 publications

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“…There have been both experimental and computational efforts in tracing the origin of these traps and quantifying their density and energies, including traps due to the polaron effect 60 , structural disorder and cavities 61 , and chemical defects and impurities 15,16,62,63 . But a comprehensive picture of the relationship between the trapping parameters and the polymer chemistry, processing condition and the electrical ageing is still missing, posing difficulties for material design.…”

Section: Discussionmentioning

confidence: 99%

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

Huang

Schadler

2016

Journal of Applied Physics

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The high field charge injection and transport properties in reinforced silicone dielectrics were investigated by measuring the time-dependent space charge distribution and the current under dc conditions up to the breakdown field, and were compared with properties of other dielectric polymers. It is argued that the energy and spatial distribution of localized electronic states are crucial to determining these properties for polymer dielectrics. Tunneling to localized states likely dominates the charge injection process. A transient transport regime arises due to the relaxation of charge carriers into deep traps at the energy band tails, and is successfully verified by a Monte Carlo simulation using the multiple-hopping model. The charge carrier mobility is found to be highly heterogeneous due to non-uniform trapping. The slow moving electron packet exhibits a negative field dependent drift velocity possibly due to the spatial disorder of traps.

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Section: Discussionmentioning

confidence: 99%

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

Huang

Schadler

2016

Journal of Applied Physics

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“…In this work, the increased breakdown strength was suggested to be due to two factors namely, the difference between the ionisation potential of the added aromatic-alkyl molecules compared to that of the host material and the high electron affinity of such structures, which would allow aromatic-alkyl moieties to act as voltage stabilizers within the system. 56,57 While we are not aware of 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 A c c e p t e d M a n u s c r i p t any theoretical studies of charge transport through epoxy resins, this is not the case for analogues of polyethylene, where the role of both chemical and structural factors have been considered 24,[58][59][60] . In the latter case, the importance of free volume on electron transport has been demonstrated and, therefore, in addition to the direct role of the functional groups of the FNM, the impact of such species on local structure and, thereby, charge transport dynamics may also be significant.…”

Section: 25mentioning

confidence: 99%

Functional design of epoxy-based networks: tailoring advanced dielectrics for next-generation energy systems

Saeedi¹,

Vaughan²,

Andritsch³

2019

J. Phys. D: Appl. Phys.

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Epoxy resins are widely used as the primary insulation material in many demanding energyrelated applications. As such, the ability specifically to tailor the electrical performance of such systems to meet increasingly demanding insulation situations has considerable utility. This paper describes a new approach to this problem, which is based upon the controlled introduction of specific functional groups into the cured resin's network architecture. Here, two additives are considered, termed functional network modifiers (FNM), namely glycidyl hexadecyl ether and glycidyl 4-nonylphenyl ether; in all the investigated systems, the ideal stoichiometric ratio of epoxide groups to amine hydrogens is retained. In the case of both FNM, their inclusion resulted in a progressive reduction in the glass transition temperature T g of the system, a reduction in the real part of the permittivity and reduced dielectric losses wihin the accessible frequency range, increased DC conductivity and increased AC breakdown strength. The magnitude of the observed effects are found to be dependent upon the choice of functional modifier, which suggests that such changes are not related merely to the inclusion of an additive within the system, but are also influenced by the chemistry of the additive itself. Explanations for these effects are proposed. It is concluded that the use of such FNM at low concentrations (~4% in the work reported here) offers a novel alternative means of engineering advanced materials to meet the current and future needs in an adaptable and easily implemented manner.

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“…Thus, the time scale for electron trapping appears to be nearly as long or even longer than the time for the solvation of electrons in water (250-300 fs) 109 and ammonia (200±50 fs). 110 For amorphous polyethylene, the calculations of Cubero and Quirke 19 suggest that the trapping (as opposed to the initial localization) takes picoseconds. The same calculation indicates that detrapping is relatively fast (tens of picoseconds) even for relatively deep traps ( E t ≈350 meV), 19,82 as the detrapping is driven by a large increase in the entropy.…”

mentioning

confidence: 99%

“…110 For amorphous polyethylene, the calculations of Cubero and Quirke 19 suggest that the trapping (as opposed to the initial localization) takes picoseconds. The same calculation indicates that detrapping is relatively fast (tens of picoseconds) even for relatively deep traps ( E t ≈350 meV), 19,82 as the detrapping is driven by a large increase in the entropy. 19 These estimates are similar to ours for n-hexane and methylcyclohexane at 295 K (Sec.…”

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confidence: 99%

Photostimulated electron detrapping and the two-state model for electron transport in nonpolar liquids

Shkrob¹,

Sauer²

2005

The Journal of Chemical Physics

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In common nonpolar liquids, such as saturated hydrocarbons, there is a dynamic equilibrium between trapped (localized) and quasifree (extended) states of the excess electron (the two-state model). Using time-resolved dc conductivity, the effect of 1064 nm laser photoexcitation of trapped electrons on the charge transport has been observed in liquid n-hexane and methylcyclohexane. The light promotes the electron from the trap into the conduction band of the liquid. From the analysis of the two-pulse, two-color photoconductivity data, the residence time of the electrons in traps has been estimated as ca. 8.3 ps for n-hexane and ca. 13 ps for methylcyclohexane (at 295 K). The rate of detrapping decreases at lower temperature with an activation energy of ca. 200 meV (280-320 K); the lifetime-mobility product for quasifree electrons scales linearly with the temperature. We suggest that the properties of trapped electrons in hydrocarbon liquids can be well accounted for using the simple spherical cavity model. The estimated localization time of the quasifree electron is 20-50 fs; both time estimates are in agreement with the "quasiballistic" model. This localization time is significantly lower than the value of 310±100 fs obtained using time-domain terahertz (THz) spectroscopy 2.for the same system [E. Knoesel et al., J. Chem. Phys. 121, 394 (2004)]. We suggest that the THz signal originates from the oscillations of electron bubbles rather than the freeelectron plasma; vibrations of these bubbles may be responsible for the deviations from the Drude behavior observed below 0.4 THz. Various implications of these results are discussed.

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Computer simulations of localized small polarons in amorphous polyethylene

Cited by 35 publications

References 14 publications

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

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

Functional design of epoxy-based networks: tailoring advanced dielectrics for next-generation energy systems

Photostimulated electron detrapping and the two-state model for electron transport in nonpolar liquids

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