The purpose of this project is investigation of some regularities observed in macroscopic systems for confined systems. The first studied regularity is “The Law of Rectilinear Diameter”. First the equation of bulk systems was used and the diameter fitted to this equation very well. Then new parameter was used and by the bulk equation fitting was repeated. The results of studying for confined fluids showed that, the effective parameter on this law is critical temperature. How ever if the critical temperature of confined fluid is closer to the critical temperature of bulk systems this law observes up to higher temperature so the new parameter decreased and the more the effects of confinement, the more decreasing the critical temperature. In the second part critical exponents studied for confined fluids. These exponents show the relation between the thermodynamic variable around the critical point. But as the only series of data we had, were related to coexistence curve so among all the exponent ? was selected. Results showed that this exponent was related to critical density inversely and the effects of confinement cause this exponent to be reduced. The other point is that because of the difference between the temperature range for confined fluids and bulk, the value of this calculated exponent is different from the bulk value. Also this exponent is universal for bulk systems bulk in confined fluid it’s related to the fluid too. The last part of this project has involved the calculation of the direct correlation function for confined fluids. This work performed by the experimental information of structure factor function. The total behavior of this function was similar to the bulk behavior so we examined the model, were suggested by Keshavarzi and etal for bulk systems. This model could predict the bulk structure factor function in low k very well. For our project this model was useful too. Because we could calculate the structure factor function for confined systems by means of the related equation and good results were achieved by comparison the theoretical and experimental data. As we know the direct correlation function is related to structure factor function by furrier transformation. So if we made a bit mistake in calculating the direct correlation function this mistake increase extremely for structure factor function and because the results of structure factor function were very good so this model can describe confined fluid behavior very well. Finally it can be told that confined fluids obey the same laws as well as bulk systems. This results has reported for the first time.
