Sun developed a consistent atomic force field (referred to as COMPASS) that aims to be applicable to a wide range of chemistries. This Class II force field is built on the basis of quantum chemistry calculations of molecular systems, and its parameters are systematically scaled to fit the experimental data such as density and heat capacity. COMPASS was used for the prediction of the thermodynamic, structural, and vibrational properties of PDMS. Reasonable agreement with the experiment was observed in all cases. Curro and co-workers developed a refined force field at the unit-atom level to extend the accessible spatio-temporal scales of MD ismulations for PDMS materials. Good agreement was reported between experiments and simulations in pressure and structural properties. Later, Smith et al. developed a modified version of the Class II force field based purely on quantum chemistry using more complex oligomers of PDMS and at higher level of quantum chemistry calculations. Recently, Huang et al. developed an improved Class II force field for PDMS systems by combining bottom-up and top-down approaches using both quantum mechanical calculations and experimental data. Huang's model demonstrated good predictions on thermodynamic properties such as density, solubility parameter, and glass transition temperatures.