The studies employ molecular dynamics (MD) simulations of ions (K+, Na+, Ca2+, and Cl−) in aqueous solutions. We use the SPC/E model to explain water. MD simulations are used to offer a stochastic coarse-grained description of ion behaviour. It describes the position, acceleration, and velocity of the ions as a system of interconnected ordinary differential equations and stochastic equations. A description between Brownian dynamics (BD) models and all-atom MD simulations is offered by the stochastic coarse-grained model. It is applied to the development of a multiscale technique that employs (less detailed) BD simulations in the remaining computational domain and all-atom MD simulations in certain areas