Molecular dynamic simulation for studying transport characteristics of confined water between sandwiched albite-quartz systems under cyclic thermal–mechanical couplings

Abstract

In this work, we make a first attempt at performing a molecular dynamic simulation to gain insights into the transport characteristics of H2O molecules confined in sandwiched albite-quartz system, where a mechanical loading couples a thermal cycling was carried out·H2O molecules were placed within the vacuum gap of the albite-quartz slab to accomplish the sandwich model. Based on the viewpoint of energetics aspect, the coulombic interactions are the dominant contributors to the total potential energy. The diffusion coefficient, orientation parameter and hydrogen bonding were examined for analysis of the transport characteristics of confined H2O molecules. Not only the water–mineral interaction but also the substrate structure reflects the dynamics of confined H2O molecules, as evident by qualitatively analyzing the trajectories of some selected H2O molecules located in different regions. The cyclic thermal–mechanical (T-M) coupling contribute a wide band distribution after 1000th cycles instead of two distinct peaks after the 100th cycles. The decrease in amplitude occurring primarily around 1.7 Å is indicative of a weaken H-Bond and a greater rotational freedom of those molecules, leading to the gathering of H2O molecules near quartz and albite slabs and a dense arrangement of the H2O molecules in the inter-spacing region, which could be ascribed to the interconnected aspect of diffusion process.