Molecular dynamics simulations are used to study structural and dynamic properties of water and aqueous uranyl ion adsorbed in a slit-like pore of amorphous silica. Calculations are performed for the flexible SPC/E water model in the atomistically detailed pores with sizes in the range of 2.0-5.0 nm. The hydroxyl groups on the pore surfaces lead to a strong adsorption and strongly affect the mobility of water molecules. The uranyl ion and its aqueous environment adsorbed in the pores are studied at the room temperature for different amounts of water. The effect of hydroxylated silica pores on the formation of uranyl hydrate complexes is discussed within the present study.

Molecular dynamics (MD) simulations are reported for a Lennard-Jones fluid adsorbed into a model silica gel to study the dynamic properties of the adsorbed methane molecules. The mean-square displacement and velocity autocorrelation function of the adsorbed molecules are calculated for a set of supercritical temperatures at low (gas-like) and high (liquid-like) fluid densities and compared with the same data for a bulk fluid. The evaluated radial distribution functions illustrate the formation of a contact layer on the pore surface that is consistent with the decrease in the mobility of the adsorbed molecules in a porous environment. The calculated self-diffusion coefficient indicates a good quantitative agreement with the measured data for methane confined to the silica gel.