Npj Comput. Mater.: 超快激光的妙手真可“点石（墨）成金（刚石）”
海归学者发起的公益学术平台
分享信息，整合资源
交流学术，偶尔风月
超快激光在控制材料的结构和性能方面有着广泛的应用。近年来，光诱导的结构相变引起了人们的极大关注。碳是自然界中最重要的元素之一，可以形成大量的有机和无机物质。其中，石墨和金刚石分别是碳在常压和高压下最稳定的结晶固相。石墨是一种具有强平面内sp2杂化共价键和弱层间范德华相互作用的原型层状晶体，而金刚石由纯sp3杂化键组成。由于巨大的动力学屏障，从石墨到金刚石的转换是极具挑战性的。除了利用高温高压条件驱动这种转变，超快激光也被发现具有诱导sp2-to-sp3键转变的潜力。实验测量发现，强激光作用后，石墨样品中表现出层间收缩和成键的特征。然而，由于当时探测技术的空间和时间分辨率相对粗糙，相变过程中的晶格演变以及非平衡载流子动力学过程都还是“点石成金”路上的未知领域，等待进一步的探索和揭密。
图1激光诱导石墨结构相变的三阶段示意图。
Driving forces for ultrafast laser-induced sp2 to sp3 structural transformation in graphite
Chenchen Song, Mengxue Guan, Yunzhe Jia, Daqiang Chen, Jiyu Xu, Cui Zhang & Sheng Meng
Understanding the microscopic mechanism of photoinduced sp2-to-sp3 structural transformation in graphite is a scientific challenge with great importance. Here, the ultrafast dynamics and characteristics of laser-induced structural transformation in graphite are revealed by non-adiabatic quantum dynamic simulations. Under laser irradiation, graphite undergoes an interlayer compression and sliding stage, followed by a key period of intralayer buckling and interlayer bonding to form an intermediate sp2-sp3 hybrid structure, before completing the full transformation to hexagonal diamond. The process is driven by the cooperation of charge carrier multiplication and selective phonon excitations through electron-phonon interactions, in which photoexcited hot electrons scattered into unoccupied high-energy conduction bands play a key role in the introduction of in-plane instability in graphite. This work identifies a photoinduced non-adiabatic transition pathway from graphite to diamond and shows far-reaching implications for designing optically controlled structural phase transition in materials.
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