Water-formamide mixtures: Topology of the hydrogen-bonded network

A neutron diffraction measurements and molecular dynamics simulations have been performed to study the hydrogen bonded structure of water-formamide mixtures. We showed that the calculated and measured total neutron diffraction radial distribution function agreed very well. After evaluation of this function, the hydrogen-bonded structure of mixtures with various compositions has been studied, and the clustering properties and the topology of the hydrogen-bonded network were investigated. The results show that these mixtures exhibit an extended range structure in solution. In water-formamide mixtures the average number of hydrogen bonded neighbors (water, formamide) and the distribution of the number of H-bonded neighbors do not change significantly as a function of the formamide mole fraction. Molecules are shown to form percolated networks at each concentration. The composition of cyclic entities in these systems is very close to being ideal; that is, these systems are microscopically homogeneous.