A Combined Monte Carlo and Hückel Theory Simulation of Orientational Ordering in C60 Assemblies

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• 作者：Jeremy Leaf ; Andrew Stannard ; Samuel P. Jarvis ; Philip Moriarty ; Janette L. Dunn
• 刊名：Journal of Physical Chemistry C
• 出版年：2016
• 出版时间：April 21, 2016
• 年：2016
• 卷：120
• 期：15
• 页码：8139-8147
• 全文大小：566K
• 年卷期：0
• ISSN：1932-7455

文摘

Orientational ordering of C₆₀ 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 Hückel theory methods and compare to experimental data. A measure of the repulsive interaction energy between two adjacent C₆₀ 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 C₆₀ 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.