Non-exponential kinetic behavior of confined water

TL;DR

This study uses molecular dynamics simulations to explore how water confined in silica pores exhibits non-exponential, slow dynamics influenced by hydration levels, challenging traditional diffusion models.

Contribution

It provides new insights into the non-exponential kinetic behavior of confined water and highlights the impact of hydration on its dynamics near hydrophilic surfaces.

Findings

Confined water shows slow, non-exponential dynamics at low hydration levels.

Decreased hydration leads to a cage effect, slowing water molecule movement.

Traditional stochastic diffusion models do not apply to this confined water system.

Abstract

We present the results of molecular dynamics simulations of SPC/E water confined in a realistic model of a silica pore. The single-particle dynamics have been studied at ambient temperature for different hydration levels. The confinement near the hydrophilic surface makes the dynamic behaviour of the liquid strongly dependent on the hydration level. Upon decrease of the number of water molecules in the pore we observe the onset of a slow dynamics due to the ``cage effect''. The conventional picture of a stochastic single-particle diffusion process thus looses its validity.