Abstract
We carry out a systematic micro-structural characterization of the solidfluid
interface (SFI) of water and simple metal chloride aqueous solutions
in contact with a free standing plate or with two such plates separated by
an inter-plate distance 0 ! h(Å) ! 30 at ambient conditions via isothermalisobaric
molecular dynamics. With this characterization we target the
interrogation of the system in search for answers to fundamental questions
regarding the structure of the ‘external’ and ‘internal’ (confined) SFI’s, the
effect of the differential hydration behavior among species and its link to
species expulsion from confinement. For water at ambient conditions we
found that the structure of the ‘external’ SFI’s is independent of the interplate
distance h in the range 0 ! h(Å) ! 30 , i.e., the absence of wallmediated
correlation effects between ‘external’ and ‘internal’ SFI’s, and
that for h < 9Å the slit-pores de-wet. Moreover, we observed a selective
expulsion of ions caused by the differential hydration between the anion
and the cations with a consequent charging of the slit-pore. All these
observations were interpreted in terms of the axial profiles for precisely
defined order parameters including tetrahedral configuration, hydrogen
bonding, and species coordination numbers.