(592a) Molecular Simulations of Polycyclic Aromatic Compounds

Abstract

Detailed information of thermodynamic properties like density, vapour pressure and vaporisation enthalpy, and dynamic properties as viscosity, of fuels in diesel engines under working conditions are hard to obtain, as a result of the high temperatures (up to 750 K) and pressures (250 MPa) that reign in the engine, making experimental measurements almost impossible to realise.  Recently, it has been shown for the benzene molecule that empiric simulations applying Anisotropic United Atom (AUA) intermolecular potential need to explicitly take into account electrostatic interactions to obtain accurate viscosities [1].

Extension of this approach to polycyclic aromatic hydrocarbon molecules (with cycles ranging from 2 to 4, cf. Figure 1), which are important constituents of diesel fuels is now under progress. Electrostatic interactions were included using point charges that were derived from renormalized quadrupole moments based on quantum mechanical calculations. 

Figure 1

In this communication we report the systematic optimisation of these point charges in order to reproduce thermodynamic and dynamic properties of the pure compounds, predicted by means of Gibbs ensemble Monte Carlo and MD simulations and compared to the experimental data available. Finally, we have used the optimised potential to predict the viscosity of polycyclic aromatic molecules for which no experimental data are available.

[1]  Bonnaud P.; Nieto-Draghi C.; Ungerer P. J. Phys. Chem. B 2007, 111, 3730.