Structure and dynamics in aqueous mixtures of glycerol: insights from molecular dynamics simulations

Aqueous glycerol mixtures are investigated over the whole concentration range of glycerol x_GLY = 0.1-0.9 via molecular dynamics (MD) simulations at ambient pressure and temperature. Two glycerol force fields are used: an all-atom (AA) and a united-atom (UA) model. Structural changes upon different mixing ratios are discussed through the site-site radial distribution functions (RDFs), coordination numbers and cluster analysis. As both species are hydrogen bonded, they form an almost perfect H-bonded network, with no observed clusters. There are, however, noticeable changes in the RDFs. Glycerol correlations grow stronger with increasing glycerol content, as do water correlations. There is significant transformation in dynamics as well, as evidenced by the self-diffusion coefficients, the velocity autocorrelation functions and the rotational autocorrelation functions. Diffusion of both species slows down with increasing glycerol content. Rotational relaxation is also altered depending on the mixture composition and there is a slow-down at the lower end of glycerol content.