Trevethan Thomas, Latham Christopher D, Heggie Malcolm I, Briddon Patrick R, Rayson Mark J
Department of Chemistry, University of Surrey, Guildford, GU2 7XH, UK.
Nanoscale. 2014 Mar 7;6(5):2978-86. doi: 10.1039/c3nr06222h. Epub 2014 Feb 3.
The formation of extended defects in graphene from the coalescence of individual mobile vacancies can significantly alter its mechanical, electrical and chemical properties. We present the results of ab initio simulations which demonstrate that the strain created by multi-vacancy complexes in graphene determine their overall growth morphology when formed from the coalescence of individual mobile lattice vacancies. Using density functional theory, we map out the potential energy surface for the motion of mono-vacancies in the vicinity of multi-vacancy defects. The inhomogeneous bond strain created by the multi-vacancy complexes strongly biases the activation energy barriers for single vacancy motion over a wide area. Kinetic Monte Carlo simulations based on rates from ab initio derived activation energies are performed to investigate the dynamical evolution of single vacancies in these strain fields. The resultant coalescence processes reveal that the dominant morphology of multi-vacancy complexes will consist of vacancy lines running in the two primary crystallographic directions, and that more thermodynamically stable structures, such as holes, are kinetically inaccessible from mono-vacancy aggregation alone.
单个移动空位合并形成的石墨烯扩展缺陷会显著改变其机械、电学和化学性质。我们展示了从头算模拟的结果，这些结果表明，石墨烯中多空位复合体产生的应变决定了它们由单个移动晶格空位合并形成时的整体生长形态。利用密度泛函理论，我们绘制了单空位在多空位缺陷附近运动的势能面。多空位复合体产生的不均匀键应变在很大范围内强烈影响单空位运动的活化能垒。基于从头算得出的活化能速率进行动力学蒙特卡罗模拟，以研究这些应变场中单个空位的动态演化。由此产生的合并过程表明，多空位复合体的主要形态将由沿两个主要晶体学方向延伸的空位线组成，而且仅靠单空位聚集在动力学上无法形成更热力学稳定的结构，如孔洞。
