Water confined in Vycor glass. II. Excluded volume effects on the radial distribution functions

Abstract

The results of a recent neutron diffraction experiment on water confined in Vycor glass, reported in the preceding paper [F. Bruni, M. A. Ricci, and A. K. Soper, J. Chem. Phys. 109, 1478 (1998)], are analyzed by attempting to correct for the distortions brought into the site–site radial distribution functions by the presence of regions of the sample where water molecules are not allowed. These so-called excluded volume effects are evaluated through calculation of the radial distribution function of a uniform fluid in the same confinement conditions as our water samples, and are shown to have a strong effect on the relative intensity of the peaks of the site–site distribution functions. The corrected data are compared with corresponding data on bulk water where appropriate, suggesting that confinement in porous Vycor glass strongly affects the orientational arrangements of water molecules, even at room temperature. The general consequences of this analysis for diffraction studies of other confined liquids, as well as water, are discussed.