Authors: Dongping Chen, Tim Totton, Jethro Akroyd, Sebastian Mosbach, and Markus Kraft*

The size-dependent melting behaviour of clusters of polycyclic aromatic hydrocarbon (PAH) molecules is studied computationally using the isotropic PAHAP potential (Totton et al., 2012, Phys Chem Chem Phys, 14, 4081–4094). The investigation aims to shed light on the understanding of the liquid-like behaviour of PAH clusters. Detailed molecular dynamic (MD) simulations are performed to investigate the size-dependent melting of two representative homogeneous PAH clusters composed of either pyrene (C₁₆H10) or coronene (C₂₄H₁₂) molecules. The evolution of the intermolecular energy and the Lindemann index are used to estimate the melting points of individual nano-clusters. The results from the MD simulations show that individual PAH molecules within nano-clusters are highly mobile below typical flame temperatures. A detailed morphological investigation of coronene₅₀₀ further reveals that the coronene clusters evolve from a columnar particle in the solid phase to an irregular spherical particle in the liquid phase. In contrast, no such evolution is observed for pyrene₃₀₀ which remains in a spherical configuration. The nano-cluster reduced melting temperature decreases with decreasing particle size following a linear relation with reciprocal size. The melting process of these clusters starts from the surface and the liquid layer grows inwards with increasing temperature.

• This paper draws from preprint 130: Size-dependent melting of polycyclic aromatic hydrocarbon (PAH) nano-clusters: A molecular dynamics study
• Access the article at the publisher: DOI: 10.1016/j.carbon.2013.09.058

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