A Combined Monte Carlo and Huckel Theory Simulation of Orientational Ordering in C60 Assemblies
A Combined Monte Carlo and Huckel Theory Simulation of Orientational Ordering in C60 Assemblies
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DOI：
10.1021/acs.jpcc.6b00638
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发表时间：
2016-04-21
影响因子：
3.7
通讯作者：
Dunn, Janette L.
中科院分区：
文献类型：
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作者：
Leaf, Jeremy;Stannard, Andrew;Dunn, Janette L.
单层和多层岛内 C-60 分子的定向排列是扫描隧道显微镜 (STM) 研究中经常观察到的现象。在这里，我们通过蒙特卡罗和休克尔理论方法的新颖组合来模拟 STM 图像中看到的方向排序，并与实验数据进行比较。通过估计和处理两个相邻 C-60 分子之间的电子密度分布来预先计算两个相邻 C-60 分子之间的排斥相互作用能的量度。分子取向的许多组合被认为涵盖了分子轨道的所有细节。将预先计算的分子间相互作用能量输入到模拟的 C-60 岛中。这里，每个分子的中心位置是固定的，但允许分子绕其中心自由旋转。通过顺序随机挑选分子并根据其邻居旋转它们来寻找总岛自由能的最小值。结果显示，各种不同基材上的单层和多层岛的特征与实验观察到的特征具有显着相关性。
Orientational ordering of C-60 molecules within monolayer and multilayer islands is a regularly observed phenomenon in scanning tunneling microscopy (STM) studies. Here we simulate the orientational ordering seen in STM images via a novel combination of Monte Carlo and Huckel theory methods and compare to experimental data. A measure of the repulsive interaction energy between two adjacent C-60 molecules is precalculated by estimating and processing the electron density distribution between them. Many combinations of molecular orientations are considered to encompass all the details of the molecular orbitals. Precalculated intermolecular interaction energies are inputted into a simulated C-60 island. Here, the center position of each molecule is fixed, but the molecules are allowed to rotate freely around their centers. A minimum in the total island free energy is sought by sequentially picking molecules at random and rotating them according to their neighbors. Results show significant correlation with experimentally observed features in both mono- and multilayered islands on a variety of different substrates.