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Qualitative Views on the Polyradical Character of Long Acenes

机译:关于长射精的多大特征的定性视图

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摘要

Spin-symmetry breaking appears in the DFT treatment of polyacenes, beyond a certain length, the critical length depending on the exchange-correlation potential. This phenomenon may be attributed to an instability with respect to HOMO-LUMO mixing, which suggests a diradical character of long acenes. However, the increase of the S-2 operator with acene length questions this simple view. It is shown that this increase cannot be attributed to spin polarization of the inner MOs, and that a second symmetry breaking takes place for the pentadecacene, with four unpaired electrons centered at the first and third quarters of the chain. The spin density distributions of broken-symmetry solutions support a qualitative picture in terms of tetra-methylene hexacenes separated by Clar sextets. A strategy is proposed to identify local symmetry breaking in polyradical systems.
机译:旋转对称性破裂出现在多粒的DFT处理中,超出一定长度,临界长度取决于交换相关电位。 这种现象可以归因于相对于同性恋混合的不稳定性,这表明了长酰基的Diradical特征。 然而,S-2运营商的增加与Acene Leader的问题这一简单的视野。 结果表明,该增加不能归因于内部MOS的自旋极化,并且对戊二烯的第二个对称性破碎发生,其中四个不配对的电子在链条的第一和第三季度以第一和第三季度为中心。 破裂对称溶液的旋转密度分布支持通过Clar Sextets分离的四甲基六丙烯的定性图像。 提出了一种策略来识别在多个系统中的局部对称性突破。

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