Simulating the morphology of clusters of polycyclic aromatic hydrocarbons: The influence of the intermolecular potential

Partitioning of polycyclic aromatic hydrocarbons in heterogeneous clusters

“…stacked morphologies, predicted by global optimisation methods and MD studies using the isoPAHAP force field [22,10,27], have been confirmed recently using scanning tunnelling microscopy of coronene clusters [36].…”

“…Cluster stability and morphology are sensitive to the energies and potential functional form and therefore specific potentials, such as isoPAHAP, are better able to capture PAH system behaviour compared to generalised hydrocarbon potentials [26,27,22].…”

Ion-Induced Soot Nucleation Using a New Potential for Curved Aromatics

“…An isotropic PAH potential (isoPAHAP) was developed using high accuracy intermolecular interaction energies from symmetry-adapted perturbation theory based on density functional theory (SAPT(DFT)) (Misquitta et al, 2005;Hesselmann et al, 2005;Podeszwa and Szalewicz, 2008) to provide an accurate description of intermolecular interactions of PAHs (Totton et al, 2010(Totton et al, , 2012. This potential was an improvement from previous general hydrocarbon potentials, such as the Lennard-Jones (van de Waal, 1983) and Williams' (Williams, 1999(Williams, , 2001) (W99) potentials, particularly at the T-shaped dimer geometries (Totton et al, 2010;Pascazio et al, 2017).…”

“…In such systems there are no substantial local dipole terms within the PAH and the contributions from the quadrupolar terms are relatively minor compared to the dispersion and exchange-repulsion contributions. Consequently this model has been used successfully in a number of studies of PAH systems (Chen et al, 2014b,a;Grancic et al, 2016;Pascazio et al, 2017;Bowal et al, 2018). However in cPAH molecules, strain at the carbon sites results in charge polarisation through the flexoelectric effect, and this leads to the formation of local dipole moments at the carbon atoms in the interior of the molecule.…”

Mechanical Properties of Soot Particles: The Impact of Crosslinked Polycyclic Aromatic Hydrocarbons

“…All the above mechanisms are believed to take part in the soot formation process, but their relative importance or feasibility at different conditions and temperatures is still unclear. Previous studies utilising different atomic simulation methods, such as density functional theory (Zhang et al, 2014), molecular dynamics (MD) (Schuetz and Frenklach, 2002;Totton et al, 2012Totton et al, , 2010Chung and Violi, 2011;Iavarone et al, 2017;Pascazio et al, 2017;Mao et al, 2017Mao et al, , 2018, Monte Carlo (Rapacioli et al, 2005) and well-tempered metadynamics simulations Violi, 2018, 2013) have shown that the physical interactions between medium-sized PAH are not strong enough to stabilise clusters at high temperatures, and only aromatic molecules as big as circumcoronene are able to cluster at temperatures where soot forms (≈1500 K). Understanding the degree of crosslinking in soot particles could then be important for determining which mechanisms are involved in their growth and potentially help in understanding their inception process.…”