独立γ-石墨二炔分子线的金属有机相和半导体共价相
Metallic Organometallic and Semiconducting Covalent Phases of Free-Standing $γ$-Graphdiyne Molecular Wires
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中文总结 AI 辅助
本研究通过第一性原理计算，揭示独立γ-石墨二炔分子线的金属有机相（一维金属）与共价相（带隙2.02 eV的半导体）的本征性质及力学、振动特征，为相区分提供诊断依据。
中文摘要 AI 辅助
结合sp与sp²杂化的一维碳同素异形体为具有可调电子、振动和力学响应的原子级精确量子线提供了多功能平台。近期的表面合成已在Au(100)上实现了γ-石墨二炔分子线的两种可相互转化相，二者共享相同的芳香主链但连接化学结构不同：一种是带有C-Au-C桥的金属有机中间体，另一种是带有二炔连接基的全共价产物。尽管实验技术可表征表面周期性和C≡C拉曼特征，但独立分子线的本征性质仍无法获取。本研究采用杂化泛函第一性原理计算解决这一缺口。共价相为半导体，带隙为2.02 eV，聚炔键长交替为0.117 Å，链周期性与实验值偏差在-0.5%以内；金属有机相则表现出部分累积化和一维金属行为，存在自旋通道穿过费米能级。两种孤立聚合物均表现出动态稳定性，杨氏模量分别为995 nN和861 nN，其中C-Au-C桥作为柔性连接，在宏观应变为+6%时可吸收9.2%的轴向变形。物种分辨振动分析识别出共价相在1408 cm⁻¹处的有效共轭坐标带，以及中间体在400 cm⁻¹以下的Au投影模式，为热或化学转化过程中的相区分提供了诊断指纹。
英文摘要
One-dimensional carbon allotropes combining sp and sp2 hybridizations provide a versatile platform for atomically precise quantum wires with tunable electronic, vibrational, and mechanical responses. Recent on-surface synthesis has realized the $γ$-graphdiyne molecular wire on Au(100) in two interconvertible phases sharing an identical aromatic backbone but distinct linkage chemistry: an organometallic intermediate with C-Au-C bridges and a fully covalent product with diacetylenic linkages. While experimental techniques characterize the on-surface periodicity and C$\equiv$C Raman signatures, the intrinsic properties of the free-standing wires remain inaccessible. Here, we address this gap using hybrid-functional first-principles calculations. The covalent phase is a semiconductor with a direct band gap of 2.02 eV, a polyynic bond-length alternation of 0.117 Å, and a chain periodicity reproducing experiment within -0.5%. Conversely, the organometallic phase exhibits partial cumulenization and 1D metallic behavior, with spin channels crossing the Fermi level. Both isolated polymers demonstrate dynamic stability with Young's moduli of 995 nN and 861 nN, respectively, where the C-Au-C bridge acts as a soft link absorbing 9.2% of axial deformation at +6% macroscopic strain. Species-resolved vibrational analysis identifies an effective-conjugation-coordinate band at 1408 cm$^{-1}$ for the covalent phase and Au-projected modes below 400 cm$^{-1}$ for the intermediate, offering diagnostic fingerprints for phase discrimination during thermal or chemical conversion.
发表机构
- University of Brasília（巴西利亚大学）
- State University of Campinas（坎皮纳斯州立大学）
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