Estimation by a SAFT-based density functional theory of the structure and thermodynamic properties of water films confined between graphite slices and an ice crystal

Abstract

In this study, a water model has been formulated within the framework of classical density functional theory coupled with the SAFT-VR Mie–HS approach in the bulk. It is first used to evaluate the phase behavior of confined water in carbon slit pores for molecular-thick films and over a wide range of thermodynamic conditions, thanks to the low computational cost of the method. Interestingly, both capillary condensation and capillary evaporation were detected, with their occurrence strongly dependent on the water pore size commensurability and the thermodynamic conditions. Then, the focus is performed on the thin water film confined between an ice crystal and a graphitic surface, as it is assumed that the pressure exerted by the latter could initiate mechanical damage in nanoporous materials. The similarities and differences with the previous system, i.e., graphite–water film–graphite, are highlighted. The extremely high pressures found in the water monolayer-thick film near experimental freezing conditions, together with their significant variation depending on the film thickness, could indeed explain the deformation and cracking of the nanoporous structure during ice crystal growth.