Fig. 1: Distribution of surface ions and water molecules.
From: Molecular insight into the initial hydration of tricalcium aluminate
a Snapshot for the distribution of surface ions and water molecules. b Number density of H2O, Ca and Al projected to z-axis. c Density ratio (\(\rho \left({O}_{w}\right)/\rho \left({H}_{w}\right)\)) and atomic excess (\(\triangle \rho\)) of H2O projected to z-axis. d Radial distribution function (RDF, g(r)) of various ion pairs (the shaded region delineates the low coordination of Ot-Hw, Al-Ow and Ca-Ow, and is magnified in the upper right corner) and (e) the corresponding coordination numbers (CNs). Number density of (f) Hw and (g) Ow within the interface region (~14–21 Å) projected to xy plane. For clarity, we denote Ow (Hw) as the oxygen (hydrogen) ions of water molecules, and Ot represents the oxygen ions on the C3A surface. Notably, Ot can be further categorized into bridging and non-bridging oxygen ions (Ob and Onb) within the AlO4 six-membered rings. The dynamic distribution of surface ions and water molecules are ensemble-averaged during a ~ 20 ps production run following a ~21 ps pre-equilibrium process. The surface line (vertical red dashed line) is determined based on the average positions of the outermost Al ions and used to define the distribution of water molecules in the vicinity regions (layers I – V divided by the vertical bule dashed lines) of the surface in the assistant of density ratio and atomic excess of H2O. The horizontal red dashed line in (c) denotes the zero value of atomic excess and serves to delineate the bulk water region (i.e., layer IV).
