Refined force field for liquid sulfolane with particular emphasis to its transport characteristics

Abstract

An all-atom force field dedicated to capturing the properties of multifunctional sulfolane is necessary. In addition to being an excellent solvent and extractor, sulfolane is also a frequently investigated component for battery electrolytes in recent times. Given this, theoretically capturing its transport properties is essential. However, given the rather high shear viscosity of liquid sulfolane and its polar aprotic nature, formulating an appropriate non-polarizable force field for this compound remains a challenge. Starting from a generic force field, we report a refined force field for sulfolane which quantitatively captures its bulk properties, resulting in significantly improved estimates for self-diffusion constant and shear viscosity of sulfolane in comparison to force fields reported hitherto. Density, self-diffusion constant, and shear viscosity were determined between temperatures (303 and 398) K and at 1 bar pressure. All properties determined from the refined force field are in good agreement with experiments. The refined model employs atomic site charges obtained from the density-derived electrostatic and chemical (DDEC6) method for liquid sulfolane modeled using quantum density functional theory. Lennard-Jones parameters were refined using quantum potential energy scans. Despite possessing a large dipole moment, the large molecular size of sulfolane partially disrupts intermolecular dipolar ordering in liquid sulfolane. Molecular dipoles of near neighbor sulfolane, however, retain a partial preference for antiparallel orientation even at the highest temperatures investigated here.