Issue 26, 2015

Phase changes of the water hexamer and octamer in the gas phase and adsorbed on polycyclic aromatic hydrocarbons

Abstract

We investigate thermodynamic properties of small water clusters adsorbed on polycyclic aromatic hydrocarbons (PAHs), which are relevant systems in the context of astrophysical and atmospheric chemistry. We present heat capacity curves computed from parallel-tempering molecular dynamics and Monte Carlo simulations that were performed using the self-consistent-charge density-functional based tight-binding method. These curves are characteristic of the phase changes occurring in the aggregates and provide useful information on the evolution of the interaction between the water molecules and the PAHs as a function of temperature. After benchmarking our approach on the water hexamer and octamer in the gas phase, we present some results for these same clusters adsorbed on coronene and circumcoronene. When compared to the curves obtained for the isolated water clusters, the phase change temperature significantly decreases for the (H2O)8–PAH clusters whereas it depends on the nature of the PAH in the case of the hexamer. We analyse these differences as connected to the relative energies of the optimized characteristic isomers and to their dynamical behavior. We also evidence the population changes of the various cluster isomers as a function of temperature.

Graphical abstract: Phase changes of the water hexamer and octamer in the gas phase and adsorbed on polycyclic aromatic hydrocarbons

Supplementary files

Article information

Article type
Paper
Submitted
10 Apr 2015
Accepted
03 Jun 2015
First published
03 Jun 2015

Phys. Chem. Chem. Phys., 2015,17, 17079-17089

Author version available

Phase changes of the water hexamer and octamer in the gas phase and adsorbed on polycyclic aromatic hydrocarbons

L. F. L. Oliveira, J. Cuny, M. Morinière, L. Dontot, A. Simon, F. Spiegelman and M. Rapacioli, Phys. Chem. Chem. Phys., 2015, 17, 17079 DOI: 10.1039/C5CP02099A

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