Evaluation of Relative Permittivity Using MD

Using the full atomistic model to perform MD calculations, the relative permittivity at a temperature of 300 K has been evaluated for water, octane, benzene, ethanol, and methanol. Calculations for water are made using the SPC-FW model. All other molecules were calculated using J-OCTA modeling (GAFF was used for the force field values, and MO calculations were used for the charge values). A single composition system is created for each molecule. The number of molecule is set to about 700 particles, and the boundary was set to periodic boundary conditions. The MD calculations were made using our solver VSOP.
After performing MD calculations with the NTP ensemble at 300K and relaxing the system, further calculations were performed to obtain time series data for the evaluation of relative permittivity. The relative permittivity computations were made using the following formula^[1].

Figure 1 shows a comparison between relative permittivity experimental data and the results obtained through the MD estimations. The simulation results are close to the experimental results. However for materials with small electron bias inside molecules such as octane and benzene, the estimated relative permittivity values have a tendency to be low.

Figure 1 Comparison of Relative Permittivity Values Obtained from MD Calculations Estimations Against the Experimental Data

Table 1 Density and Relative Permittivity - Experimental Data and MD Estimations

	ρMD [g/cm^3]	εMD[-]	ρexp [g/cm^3]	εexp^[1,2] [-]
water	1.01	77.7	1.00	88.2
octane	0.69	1.06	0.70	1.95
benzene	0.85	1.04	0.88	2.28
methanol	0.83	35.2	0.79	32.6
ethanol	0.82	22.1	0.79	24.3

Reference
[1] N. Yoshii, S. Miura, S. Okazaki, Chem. Phys. Lett. 345 (2001) 195-200
[2] Chronological Scientific Tables 2005 Maruzen
[2] Chemistry Handbook 2004 Maruzen

Please feel free to contact us if you have any questions or comments.

HOME > Case Studies > Evaluation of Relative Permittivity Using MD