Prediction of Henry's law constants of small gas molecules in liquid ethylene oxide and ethanol using force field methods

Widom insertion method coupled with canonical ensemble (NVT) molecular simulations based on different force fields was utilized to calculate Henry's law constants (HLCs) of several common gas molecules, N2, O2, CH4, and CO2, in liquid ethylene oxide and ethanol. Several simulation options, including insertion grid densities, liquid densities, force field models, and simulation methods were investigated. The results indicate that reasonably good agreements between the calculated and experimental values were obtained using the united-atom (UA) model. However, systematically overestimated values are obtained with the all-atom (AA) force field model. The causes of the problems were investigated comparatively. The data indicate that hydrogen atoms in the AA model are mainly responsible for these problems, but the underlying sampling algorithm in Widom insertions, which may be the real source of problems, needs further investigation.