6533b7dafe1ef96bd126deb3

RESEARCH PRODUCT

Molecular simulation of mixed gas hydrates in astrophysical conditions

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description

In this PhD work, numerical simulation methods have been used in order to model clathrate hydrates at the molecular scale, in thermodynamic conditions typical of astrophysical contexts. The aim was to characterize the trapping abilities of those peculiar structures of water, by means of the tools used in adsorption studies. The results presented in the present thesis are focused on a couple of chemical species which are found to be abundant in our astrophysical vicinity and are quite similar: carbon monoxide, CO, and nitrogen, N2. Thus, the single-component clathrates of CO and N2, and the mixed hydrate CO-N2 have been studied, mainly using grand canonical Monte Carlo simulations. First, these clathrates have been examined as part of a bulk phase. A preferential encapsulation of CO molecules, with respect to N2 molecules, has been highlighted in the simulations, in agreement with recent experimental data and thermodynamic calculations. Secondly, the hydrate systems have been brought in contact with a gaseous interface in order to study the surface adsorption of CO and N2 molecules. Simulations with other forms of solid water, also found in astrophysical contexts, have been performed. All the considered surfaces have shown a greater molecular selectivity towards the trapping of CO molecules, compared to the one of hydrates' cages.