Atomistic Modeling of the Structural and Dynamic Properties of Aqueous NaCl and Na2SO4 Solutions in the Interlayer Space of Ettringite

The use of a new modification of the ClayFF force field for molecular dynamics modeling of ettringite crystals and interaction of aqueous NaCl and Na2SO4 solutions with their surface shows that the possibility of explicitly taking into account metal-O-H interactions in the system leads to the formation of stronger hydrogen bonds in the crystal structure and on the surface and to greater localization of the atoms of both the crystalline phase and solutions in the subsurface zone. The relative fractions of the inner- and outer-spheric adsorption of Na+, Cl-, and (SO4)(2-) ions and the mobility of H2O molecules in both solutions also change. The calculated crystal lattice parameters and the density of ettringite remained almost unchanged between the old and new versions of the ClayFF force field, but the accuracy of reproduction of the elastic characteristics of the crystal markedly increased.