The effect of Methanol Number molecules and force fields on self diffusion coefficient and the number of Hydrogen Bonding by Gromacs

The diffusion coefficient is indispensable to chemical engineering design and research. Inpractical engineering and research, there is still a great lack of available data. Therefore,methods need to be developed to solve this problem[1,2]. In this paper, analytical method anda molecular dynamics simulation method by using the Einstein relation (MSD) are used topredict the self-diffusion coefficient for fluids.The classical molecular dynamics method can be divided into equilibrium moleculardynamics and non-equilibrium molecular dynamics. In this paper, the equilibrium moleculardynamics simulation method has been used to simulate the diffusion coefficient. The Einsteinrelation is also called the mean square displacement relation. For self-diffusion coefficients,the relationship is ?????????? The Einstein relationship and the Green–Kubo relationship are equal in theory. The term ??????? in the Einstein relation is regarded as mean square displacement (MSD).In addition to Many thermo dynamical properties (e.g., melting and boiling point) of themixture depend on the strength of the hydrogen bonds (H-bond) formed among molecules.Since methanol has one hydroxyl group, it can form such bond[3].In this work, we will investigate the effects of number of molecules and force fields onhydrogen bonding and self diffusion coefficient for methanol system by molecular dynamicsimulation. It is clear that hydrogen bonding and number of molecules influence on selfdiffusion coefficient. For comparison, for one state in the same condition is simulated for 1- octanol system similar to methanol. Thermo physical properties for these simulations andfigures are shown in the following. It shows that an increasing number of methanol moleculesincrease self-diffusion coefficient. This result may be due to reduced attractions caused bythe hydrogen bond is due to the increased number of molecules of methanol. These results areshown in tables 1 and 2.