Department of Mechanical Engineering, University of California, and Environmental Energy Technologies Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
J Phys Chem A. 2010 Jan 21;114(2):689-703. doi: 10.1021/jp906541a.
A new detailed chemical-kinetic Monte Carlo model of graphene-edge growth is presented. The model employs a fine-grained approach to chemically resolved species, allows for incorporation of five-member rings into growing structures, and links the stochastic kinetic steps to a geometry optimization, thereby properly accounting for curving of molecular structures. The evolving morphology is greatly affected by the rates of key reactions and hence by surface-site steric environment and gas-phase species concentrations. The evolving graphene morphology and growth rates seemingly reach "asymptotic" behavior, independent of the initial substrate. Most noteworthy, growing layers become significantly curved. The curvature occurs regardless of initial substrate at both 1500 and 2000 K with higher curvature occurring at the lower temperature. More intriguing is the observation that, at 2000 K, transition from planar to curved growth does not commence immediately but occurs at some later time, seemingly when the growing graphene reaches a size significantly larger than coronene. No curvature is produced in numerical simulations at 2500 K, indicating that high-energy environments cause the five-member-ring to be less stable, thus preventing them from forming.
提出了一种新的详细的石墨烯边缘生长的化学动力学蒙特卡罗模型。该模型采用了一种精细的化学分辨物种方法，允许将五元环纳入生长结构，并将随机动力学步骤与几何优化联系起来，从而正确考虑分子结构的弯曲。演化形态受关键反应速率的影响很大，因此受表面位阻环境和气相物种浓度的影响。演化的石墨烯形态和生长速率似乎达到了“渐近”行为，与初始衬底无关。最值得注意的是，生长层变得明显弯曲。这种曲率无论在 1500 和 2000 K 时的初始衬底如何都会发生，而且在较低温度下曲率更大。更有趣的是，在 2000 K 时，从平面到弯曲生长的转变不是立即开始，而是在稍后的某个时间开始，似乎是在生长的石墨烯达到比蔻烯大得多的尺寸时才开始。在 2500 K 的数值模拟中没有产生曲率，这表明高能环境导致五元环不太稳定，从而阻止它们形成。
