透過熱輔助密度泛函理論分析線性駢苯在定向外加電場下的電子性質

Abstract

在定向外加電場中，透過傳統的密度泛函理論預測線性駢苯(linear acene) 的電子性質並不是一個精確的方法。由於強關聯作用的影響，傳統的分析方 法會有較大的誤差。因此，為了預測的精準性，我們採用熱輔助密度泛函理論 (Thermally-assisted-occupation density functional theory) 來分析線性駢苯在定向外加 電場中的性質。在我們的研究結果中，我們發現隨著電場的增強，單重態三重態 能量差(singlet-triplet energy gap)、基本能隙 (fundamental gap) 會輕微的下降，而 對稱性馮諾伊曼熵(symmetrized von Neumann entropy)則有較明顯的上升。相較 於前面的結果，垂直游離能和垂直電子親和力則表現出不一樣的變化。游離能和 電子親和力的變動會因為環數的奇偶性而有所不同。當環數為奇數時，兩者皆會 隨著電場強度增加而有明顯的提升;然而，當環數為偶數時，兩者對電場的變化 較不敏感。此外，透過軌道電子佔有數(orbital occupation number)，我們可以發 現當電場增加時，電子分布也會隨之由低能量的軌域遷移至高能量的軌域。

The electronic properties of linear acene in an oriented external electric field (OEEF) are difficult to predict precisely through conventional Kohn-Sham (KS) density functional theory (DFT) owing to the strong static correlation error. We investigate the molecu- lar properties based on thermally-assisted-occupation (TAO) DFT for accuracy. In our results, the singlet-triplet energy gaps and fundamental gaps decrease slightly when the electric field strength increases. However, the symmetrized von Neumann entropy in- creases obviously. Unlike the former, the variation of vertical ionization potentials and vertical electron affinities depends on the parity of the ring number. When the number is odd, the ionization potential and electron affinity increase noticeably with the increas- ing electric field. Conversely, they change little when the number is even. In addition, we observe that the electron transitions from low-energy orbitals to high-energy orbitals according to active orbital occupation numbers when we apply the external electric field.