发表机构
School of civil engineering, Sun yat-sen University（中山大学土木工程学院）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
该研究发现裸露Ti3C2 MXene的金属-碳骨架可发生键切换重构，通过双轴应变弛豫得到稳定多形体，重构可调控其电子性质，且键切换是MXene的可控结构自由度。
AI 中文摘要
MXene的性质通常通过组成、表面终止和插层来调控，而金属-碳骨架拓扑被认为是固定的。本文证明该骨架可以发生重构。双轴应变裸露Ti3C2的无约束弛豫得到了动态稳定的多形体N，其具有15个原子的原胞、6种不同的Ti-C键类，以及2.55 Å的Ti-Ti对。相干转变路径跨越每个原胞8.47 eV的势垒，但首先到达另一个重构的极小值N'，其能量比N低1.08 eV，揭示了一类键切换网络。相N的能量比母相高每个原胞7.58 eV。沿计算路径的反向势垒，对于N和N'分别为每个原胞1.50 eV和1.98 eV。该重构消除了母相的自旋极化，产生了非磁性金属，费米能级的态密度几乎增加了四倍。Bader和电子定域分析表明，电荷从C向Ti重新分布，与Ti-Ti配对相关。在多层结构中，重构层形成层间Ti-C键。10%的双轴张力使相能量差减半，压力在约85 GPa附近反转相序。这些结果确立了键切换重构是MXene中一种可机械调控的结构自由度。
英文摘要
MXene properties are typically tuned through composition, surface termination, and intercalation, while the metal-carbon framework topology is considered fixed. Here, we demonstrate that this framework can reconstruct. Unconstrained relaxations of biaxially strained bare Ti3C2 yield a dynamically stable polymorph, N, featuring a 15-atom primitive cell, six distinct Ti-C bond classes, and 2.55 Å Ti-Ti pairs. The coherent transformation pathway crosses an 8.47 eV barrier per cell but first reaches another reconstructed minimum, N', lying 1.08 eV below N, revealing a family of bond-switched networks. Phase N lies 7.58 eV per cell above the parent. Reverse barriers along the calculated pathway are 1.50 and 1.98 eV per cell for N and N', respectively. Reconstruction quenches the parent spin polarization, yielding a nonmagnetic metal with a nearly fourfold increase in Fermi-level density of states. Bader and electron-localization analyses suggest charge redistribution from C toward Ti associated with Ti-Ti pairing. In multilayers, reconstructed layers form interlayer Ti-C bonds. A 10% biaxial tension halves the phase-energy difference, and pressure reverses phase ordering near 85 GPa. These results establish bond-switching reconstruction as a mechanically controllable structural degree of freedom in MXenes.
Comments7 pages, 5 figures
