The structural organization of N -methyl-2-pyrrolidone + water mixtures: a densitometry, x-ray diffraction, and molecular dynamics study

A combined approach of molecular dynamics simulations, wide angle X-ray scattering experiments, and density measurements was employed to study the structural properties of N-methyl-2-pyrrolidone (NMP) + water mixtures over the whole concentration range. Remarkably, a very good agreement between computed and experimental densities and diffraction patterns was achieved, especially if the effect of the mixture composition on NMP charges is taken into account. Analysis of the inter- molecular organization, as revealed by the radial and spatial distribution functions of relevant solvent atoms, nicely explained the density maximum observed experimentally.