Multilayer graphene with a rippled structure for water desalination

The schematic illustration of the simulation box with dimensions of 21 × 61 × 174 Å3 is shown, according to this figure, the system consists of three layers of graphene as a membrane in the center of the simulation box. The graphene sheets are shown in blue colour. By separating two graphene sheets in each layer of this membrane, a gap has been created between the two sheets so that the ions and water molecules can enter into the membrane. In this article, this distance is named “gap” and the width of these spaces is represented by W. Three distances, 6, 7.5 and 9 Å are used for W. Each layer is located in a distance from the each other in the Z direction, which is represented by H, which is referred to the channel in this article. Three distances, 6, 7.5 and 9 Å are used for H. The mixture of salty water consist of 2883 water molecules and 10 pairs of sodium and chloride ions which are located on the right side of the membrane. Water molecules are shown as transparent, sodium ion and chloride ion are represented by green balloons and red balloons respectively. 217 water molecules are located on the left side of the membrane and 243 water molecules in each channel. Two graphene sheets are applied as the rigid piston, one of them is located behind the saline water and the other is located behind the fresh water region on both sides of the membrane, these pistons are shown by yellow color. The periodic boundary condition is applied in two dimensions of X and Y. Small arrows are showing the direction of 1 atm pressure and the large arrows are showing the direction of applied pressure for purification. In the first 500 ps simulation, the piston is fixed for reaching equilibration. In each multilayer membranes, the gap width and channel height are selected equal (W = H). According to the descriptions, the simulated systems consist of four individual regions: saline water, top channel, bottom channel, fresh water.62