Lab Meeting by Sergi Ruiz

Water confined in rigid structures, such as graphene slit pores [1], currently generates enormous interest because of its greatly different properties with respect to the bulk phase of water [2-5]. We performed extensive ab initio molecular dynamics simulations which disclosed stark differences in H-bonding and electronic properties of nanoconfined water in very narrow graphene slit pores, thus forming mono- and bilayers only, versus less strongly confined water versus bulk water [2]. THz spectroscopy is known to be sensitive to the hydration dynamics and H-bonding, thus providing unique spectroscopic fingerprints of those. In this work, we introduce a machinery based on three key guidelines to rigorously compute THz spectra of water that is nanoconfined within slit pores: (1) Precise pressure control inside the slit pore; (2) applying an intrinsic density correction for ab initio water; (3) parameterizing an accurate water-graphene force field to allow for exhaustive QM/MM dynamics and thus for sampling the dipole time-correlation functions.