Integrated Simulation System for Soft Materials.

The interface tension of water/octane has been evaluated by performing molecular dynamics (MD) calculations using the full atomistic model. Water calculations were made using the SPC-FW model. Octane was calculated using J-OCTA modeling (GAFF was used for the force field values, and MO calculations were used for the charge values). The MD calculations were made using our solver VSOP. As figure 1 shows, after performing relaxation calculations using an NPT ensemble for both of water and octane, a system with an interface is created by merging the water and octane systems together.

After the interface is created, calculations were performed using an NVT ensemble. The post relaxation stress values were used in the following formula to evaluate the interface tension. Figure 2 shows the changes in interface over time in a relaxed state. Although the interface tensions results have large fluctuations, when time averaged values are taken, the evaluated results were 53.3 [dyn/cm]. This compares well to the experimental data values of 51.7 [dyn/cm] ^[1].