Abdelghafar Khaled A, Choi Daniel S, Askar Khalid A
Mechanical and Nuclear Engineering Department, Khalifa University, PO Box 127788, Abu Dhabi, UAE.
Sci Rep. 2025 May 2;15(1):15334. doi: 10.1038/s41598-025-96242-w.
Lonsdaleite is a metastable hexagonal allotrope of carbon, which outperforms cubic diamond in terms of mechanical properties. Here, we investigate nitrogen vacancy center (NV) in pure lonsdaleite as well as the dual structure of diamond/lonsdaleite using the density functional theory (DFT). By examining various nitrogen vacancy (NV) center configurations, it was found that off-c-axis defects exhibit distinct elongation in certain bonds and localized strain, leading to shifts in electronic states and stronger electron-phonon interactions. Luminescence analysis highlights differences in zero-phonon line weights, indicating varied dominance of phonon side bands. Furthermore, the findings assert that NV and NV centers in lonsdaleite demonstrate the existence of two non-degenerate excited states (e & e) for the off-c-axis defect as a result of C symmetry evolution instead of C symmetry. Surprisingly, the findings demonstrate that the zero-phonon line (ZPL) falls around ~ 2.38 eV for NV, which agrees with the reported ZPL of 2.32 eV for NV in lonsdaleite from meteorites. Thereby, the current model could interpret the experimental luminescence data of diamond/lonsdaleite dual structure.
朗斯代尔石是碳的一种亚稳态六方同素异形体，其机械性能优于立方金刚石。在此，我们使用密度泛函理论（DFT）研究了纯朗斯代尔石中的氮空位中心（NV）以及金刚石/朗斯代尔石的双结构。通过研究各种氮空位（NV）中心构型，发现离c轴缺陷在某些键中表现出明显的伸长和局部应变，导致电子态发生位移并增强了电子 - 声子相互作用。发光分析突出了零声子线权重的差异，表明声子边带的主导地位各不相同。此外，研究结果表明，由于C对称性演化而非C对称性，朗斯代尔石中的NV和NV中心显示出离c轴缺陷存在两个非简并激发态（e & e）。令人惊讶的是，研究结果表明NV的零声子线（ZPL）落在约2.38 eV附近，这与陨石中朗斯代尔石中NV报道的2.32 eV的ZPL一致。因此，当前模型可以解释金刚石/朗斯代尔石双结构的实验发光数据。
