Water nanodroplets confined in zeolite pores

We provide a comprehensive depiction of the behaviour of a nanodroplet of 20 water molecules confined in the pores of a series of 3D-connected isostructural zeolites with varying acidity, by means of molecular simulations. Both grand canonical Monte Carlo simulations using classical interatomic forcefields and first-principles Car-Parrinello molecular dynamics were used in order to characterise the behaviour of confined water by computing it range of properties, front thermodynamic quantities to electronic properties such its dipole moment, including structural and dynamical information. From the thermodynamic point of vie x, we have identified the all-silica zeolite as hydrophobic, and the cationic zeolites its hydrophilic; the condensation transition in the first case was demonstrated to be of first order. Furthermore. in-depth analysis of the dynamical and electronic properties of water showed that water in the hydrophobic zeolite behaves as a nanodroplet trying to close its hydrogen-bond network onto itself, with I few short-lived dangling Oil groups. while water in hydrophilic zeolites "opens up" to form weak hydrogen bonds with the zeolite oxygen atoms. Finally, the dipole moment of confined Water is studied and the contributions of water self-polarisation and the zeolite electric field are discussed.