Theoretical Study of Electronic Structure with Planar, Cyclic, and Mobius-type Polycyclic Aromatic Hydrocarbons
Date Issued
2011
Date
2011
Author(s)
Shu, Ray-Shun
Abstract
Graphene nanoribbons with zigzag edge have broken spin symmetry ground state by the Hubbard model with unrestricted Hartree-Fock approximation. Polyacenes are narrow graphene nanoribbons with zigzag and also have broken spin symmetry states. Cyclic polyacenes can be constructed by bending polyacenes have spin polarization that similar to polyacenes. Broken symmetry states of polyacenes and cyclic polyacenes have a lower energy with large size and strong electron repulsion and can be found by constrains spin PPP calculation.
Mobius strip is only one side and can be obtained by twisting one edge of a band through 180° and then joining the ends. Mobius polyacenes have zigzag edge and therefore we predicted Mobius polyacenes also have broken spin symmetry ground state. Spin density population of polyacenes and cyclic polyacenes are alternation and therefore two edge sides of polyacenes and cyclicpolyacenes have different spin density phases. Mobius polyacenes are one side surfaces and have spin polarization and therefore Mobius polyacenes can be observed two spin density phases interface that called spin soliton. We observe geometry and spin soliton relation of Mobius polyacenes by AM1 and QCFF-PI calculation. Polyenes have bond length alternation and polyacenes favor equal bond length with edge bond. Mobius polyacene can be considered as a single polyacetylene along Mobius strip edge and Mobius polyacene have bond length difference at some location.
Subjects
Mobius
unrestricted Hartree-Fock
spin polarization
spin soliton
electron structure
Type
thesis
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