Hyung-Suk Pak

Surface tension of curved surfaces

The iteration method for calculating surface tension using the liquid partition function, developed by Changet al., is used to evaluate the surface tension of both concave and convex surfaces. Using the calculated values of surface tension, the change of vapor pressure with curvature is determined from the Kelvin equation. According to the calculations for various liquids such as Ar, N2, C6H6, C6H12, and H2O, (i) the surface tension increases with concavity and decreases with convexity of surface, and (ii) providing the radii are smaller than 10−6 cm, there are appreciable changes in surface tension.

A molecular dynamics simulation study on nematic-isotropic phase transition of rod-like molecules in NpT ensemble

The nematic–isotropic (N–I) phase transition of rod‐like molecules is investigated by molecular dynamics (MD) simulation. This study is focused on three different aspects. First, a more realistic model than a hard core system is employed. Second, the MD simulation enables us to calculate time‐dependent functions. Last, an isothermal–isobaric (NpT) ensemble is used to consider the change of volume at the N–I transition. The results of MD simulation suggest that the interatomic potential plays an important role in the N–I phase transition of rod‐like molecules. The MD simulation of the N–I phase transition of rod‐like molecules can predict the ‘‘weak first orderedness’’ accurately. Both translational and rotational diffusion coefficients of rod‐like molecules in the system with a smaller value of σ are larger than those with a larger value of σ, and the calculated rotational reorientation time of rod‐like molecules in isotropic phases lies in the 10−11–10−10 s range.