infinite identical cells. The utility of this mimic is to perform a simulation condition in such a way that the particles experience forces like they were in bulk fluid. Additionally, the number of particles in the central box, thus, remains constant. This ideal is represented in Figure 3.1. The original box contains a solute and solvent molecules which is surrounded with identical images of itself. The positions and velocities of corresponding particles in all of the boxes are identical. The common approach is to use a cubic or rectangular parallelepiped box, but other shapes are also possible, e.g., truncated octahedron. By this approach, what is in effect an infinite sized system is obtained.