[论文解读] Proton Quantum Effects on Electronic Excitation in Hydrogen-bonded Organic Solid: A First-Principles Green's Function Theory Study

Sampreeti Bhattacharya, Jianhang Xu+2 more|arXiv (Cornell University)|Feb 8, 2026

melanin and skin pigmentation被引用 0

一句话总结

本论文在 GW 计算中的 Bethe-Salpeter 方程（BSE）内使用核电子轨道（NEO）方法，研究质子量子效应如何改变氢键型类黑色素样有机晶体的电子激发，突出了几何导出和各向异性对激子的影响。

ABSTRACT

Nuclear quantum effects of protons on electronic excitations in hydrogen-bonded organic materials remains underexplored. In theoretical studies, modeling excitons in these extended systems is particularly difficult because they tend to have a large exciton binding energy and sometimes exhibit charge transfer character. We demonstrate how first-principles Green's function theory combined with the nuclear-electronic orbital method enables us to examine the nature of excitons in a prototypical organic solid of eumelanin, for which the extensive hydrogen bonds have been proposed to facilitate the formation of delocalized excitons. We investigate how the quantization of protons impacts electronic excitations. We discuss the extent to which the resulting proton quantum effects can be described as being derived from structure and how they induce molecular-level anisotropy for the excitons in the organic solid.

研究动机与目标

• Motivate understanding of nuclear quantum effects (NQEs) on electronic excitations in hydrogen-bonded organic materials.
• Demonstrate how the NEO method integrated with BSE@GW can quantify proton quantum effects on excitations.
• Assess whether observed effects are primarily geometry-derived or intrinsically electronic.
• Characterize exciton anisotropy and localization across monomer units in the crystal.
• Provide insights into how proton quantization alters exciton binding energy and spectra.

提出的方法

• Combine first-principles Green’s function theory (GW/BSE) with the nuclear-electronic orbital (NEO) approach to quantize protons.
• Compute quasi-particle energies with G0W0 and solve the BSE in the Tamm-Dancoff approximation.
• Use the NEO-DFT framework to obtain proton position expectation values and corresponding basis sets for protons.
• Analyze excitons via exciton probability density and Mulliken exciton populations on monomer units.
• Compare Std, NEO, and Std:QGeom scenarios to separate geometry-derived from direct quantum effects.
• Quantify exciton anisotropy through Mulliken populations and monitor changes across the 4 monomers in the unit cell.

实验结果

研究问题

• RQ1 质子量子效应如何影响氢键型有机固体的准粒子隙和光学隙？
• RQ2 质子量子效应对激发的几何导向性与对电子哈密顿量本质之间的关系有多大？
• RQ3 质子量子效应是否在单体单元之间诱导激子的各向异性或局部化？
• RQ4 晶体有机固体中质子量子化如何影响激子结合能？
• RQ5 NEO-BSE@GW 能否捕捉激子密度的峰值强度与分布的变化，而不仅仅是整体光谱？

主要发现

• 质子量子化将准粒子隙由 5.95 eV 降至 5.89 eV（Std → NEO）。
• 光学隙变化很小：4.49 eV（Std）对比 4.48 eV（NEO）。
• 激子结合能从 1.46 eV（Std）降至 1.41 eV（NEO）；Std:QGeom 得到 1.44 eV。
• 总体光吸收光谱形状基本不变；质子量子效应主要造成几何导向的平移，峰值强度也有少量变化。
• 当质子量子化时，激子在单体之间的各向异性增加，体现在更广的穆里肯激子群分布和特定激发态（如状态 51）的局部化模式上。
• NEO 质子引入了质子密度的离域化，同时平滑了有效势，导致电子结构比 Std:QGeom 更均匀，但并非纯几何起源。