MOLECULAR-DYNAMICS SIMULATIONS OF DIELECTRIC-PROPERTIES OF DIMETHYL-SULFOXIDE - COMPARISON BETWEEN AVAILABLE POTENTIALS

We present a molecular dynamics simulation study of the orientational correlations of molecular dipoles and dielectric properties of a serie s of recently proposed models for liquid dimethyl sulfoxide. The dipol e-dipole correlations, as measured by the dipolar symmetry projections h(110)(r) and h(112)(r), sire very similar for the models with four p artially charged sites, but differ somewhat for the potential with no charges on the methyl groups. The effects of the charges on the methyl sites upon the local ordering of the molecular dipoles are discussed by comparing the h(110)(r) projections for two models which differ onl y in their site-charge assignments. The Kirkwood g factors for the sim ulated force fields turn out all greater than unity, in disagreement w ith some experimental estimates. The dielectric constants, however, ar e in good agreement with reported experimental data. In addition, we d iscuss the wave vector (k) dependence of the longitudinal static diele ctric responses and also the single-particle molecular reorientation d ynamics,which is found to differ from model to model. Likely consequen ces of that To the dielectric relaxation of these models are briefly d iscussed. (C) 1997 American Institute of Physics.