  The structural and dynamical properties of water confined in nanoporous
silica with a pore diameter of 2.7 nm were investigated by performing
large-scale molecular dynamics simulations using the reactive force field. The
radial distribution function and diffusion coefficient of water were
calculated, and the values at the center of the pore agreed well with
experimental values for real water. In addition, the pore was divided into thin
coaxial layers, and the average number of hydrogen bonds, hydrogen bond
lifetime, and hydrogen bond strength were calculated as a function of the
radial distance from the pore central axis. The analysis showed that hydrogen
bonds involving silanol (Si-OH) have a longer lifetime, although the average
number of hydrogen bonds per atom does not change from that at the pore center.
The longer lifetime, as well as smaller diffusion coefficient, of these
hydrogen bonds is attributed to their greater strength.
