Parametrisation of a force field of acetamide for simulations of the liquid phase

Molecular dynamics simulations are performed to develop new parameters for acetamide using a systematic procedure proposed by Salas et al., where the atomic charges were fitted to reproduce the experimental dielectric constant and the Lennard-Jones parameters to match the surface tension and density. The parameters for formamide recently calculated by Perez etal. were used to obtain the new parameters of acetamide where atoms of the amine group and carbon kept the same intermolecular parameter values in both molecules. The parameters of the methyl group, taken as united atom, and the oxygen atom were fitted to reproduce the dielectric constant, surface tension and density at 358.15 K. The new set of parameters, based on the optimised potential for liquids simulations with all atoms, was able to predict results of the target properties as a function of temperature as a pure component and the dielectric constant and density of binary mixtures with water and formamide as a function of acetamide concentration at 298.15 K. The polymer chains formed by hydrogen bond interactions were analysed to understand the maximum of dielectric constant in acetamide-water mixtures.