DNA片段近价电离的格林函数耦合团簇模拟
Green's Function Coupled Cluster Simulation of the Near-valence Ionizations of DNA-fragments
摘要：
准确描述DNA的电离过程对于理解电离辐射对DNA的损伤以及探索DNA链在纳米电子学中的潜在应用至关重要。在本工作中，我们利用我们最近在超级计算设备上开发的格林函数耦合簇（GFCC）库，研究了几种鸟嘌呤$-$胞嘧啶的光谱函数（G $-$ C）碱基对结构（[G $-$ C] $_n$，$n=1-3$）首次在相对较宽的近价区（[-25.0，-5.0] eV）。我们的重点是给出一个初步的多体耦合团簇的理解和指导方针的垂直电离能（VIE），光谱轮廓，和电离功能的变化，这些系统的系统规模扩大，在这个近价区。结果表明，随着系统尺寸的增大，尽管最低VIE不断减小，但谱函数轮廓和相对峰位的变化却出乎意料地变小。进一步分析与光谱函数中最强峰相关的电离态，揭示了所考虑的G $-$ C碱基对系统的电离波函数中不可忽略的$|2h,1p\rangle$。随着G $-$ C碱基对尺寸的扩大，与G $-$ C碱基对的胞嘧啶部分的主要电离相关的主要$|2h,1p\rangle$的特征是从碱基对内胞嘧啶$π\rightarrowπ^\ast$激发到碱基对间电子激发的跃迁，这也指示了DNA系统的多体计算中的最小量子区域。
英文摘要：
Accurate description of the ionization process in DNA is crucial to the understanding of the DNA damage under exposure to ionizing radiation, and the exploration of the potential application of DNA strands in nano-electronics. In this work, by employing our recently developed Green's function coupled-cluster (GFCC) library on supercomputing facilities, we have studied the spectral functions of several guanine$-$cytosine (G$-$C) base pair structures ([G$-$C]$_n$, $n=1-3$) for the first time in a relatively broad near-valence regime ([-25.0,-5.0] eV) in the coupled-cluster with singles and doubles (CCSD) level. Our focus is to give a preliminary many-body coupled-cluster understanding and guideline of the vertical ionization energy (VIE), spectral profile, and ionization feature changes of these systems as the system size expands in this near-valence regime. The results show that, as the system size expands, even though the lowest VIEs keep decreasing, the changes of spectral function profile and the relative peak positions get unexpectedly smaller. Further analysis of the ionized states associated with the most intensive peak in the spectral functions reveals non-negligible $|2h,1p\rangle$'s in the ionized wave functions of the considered G$-$C base pair systems. The leading $|2h,1p\rangle$'s associated with the main ionizations from the cytosine part of the G$-$C base pairs feature a transition from the intra-base-pair cytosine $π\rightarrowπ^\ast$ excitation to the inter-base-pair electron excitation as the size of G$-$C base pairs expands, which also indicates the minimum quantum region in the many-body calculations of DNA systems.
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