Molecular Dynamics Simulation Of Transformation Of Limited Water And Methanol In The Two-dimensional

The molecular dynamics is a very important method of the computer simulation, which is very useful for more atoms by solving the equations of motion of classical mechanics. Physicists have been obsessed with the source of unusual nature for water. Han et al [Han2010] adopted the quasi-two-dimensional structure of the hydrophobic board to research phase transition of water, they found that there is a critical density.So my work is for the water phase transition through molecular dynamics, using two-dimensional structure in a hydrophobic plate. Three different thickness with d=0.8 nm, d=0.9 nm, d=1.0 nm in the direction of the limited. We calculate the potential energy, the radial mean square displacement MSD, horizontal density distribution TDP (z), respectively. we have the inference that there is a critical density between 1.29 g /cm³å’Œ1.23 g /cm³ , below it occuring in the first-order phase transition, and also above it becoming quasi-continuous of the phase transition at the critical density. Also wo fand that the phase transition temperature decressing with density fromρ= 1.07 g /cm³increases to1.23 g /cm³ ; the phase transition temperature increases with rising density fromρ= 1.29 g /cm³ toρ=1.48 g /cm³. By comparing the different systems within the limited thickness, the direction of limited may exist two critical values d_max and d_min, when dmin or d>d_max that will be the first order phase transition between solid-liquid; and also when d_minmax that will be the quasi-continuous between solid-liquid.Then using the same method to study the structure of methanol. From my simulation results in d=1.0 nm and d=1.2 nm, the conclusion for different densities of methanol is the same: (1) potential energy curve is continuous change, there is no mutation showed for first-order phase transformations; (2) by calculating the diffusion coefficient, wo can know there will be the phase transition of the different density for methanol with decreasing temperature; (3) through the horizontal density distribution TDP (z), we can fand that a continuous variation of the peak decreasing with increasing temperature, and also there is no mutation. We hypothesize that for the purposes of methanol, d=1.0 nm and d=1.2 nm in the d_minmax range, for that the solid-liquid phase transition becoming the quasi-continuous.