Detailed insight into the hydrogen bonding interactions in acetone-methanol mixtures. A molecular dynamics simulation and Voronoi polyhedra analysis study

Voronoi polyhedra (VP) analysis of mixtures of acetone and methanol is reported on the basis of molecular dynamics computer simulations, performed at 300 K and 1 bar. The composition of the systems investigated covers the entire range from neat acetone to neat methanol. Distribution of the volume, reciprocal volume and asphericity parameter of the VP as well as that of the area of the individual VP faces and of the radius of the empty voids located between the molecules are calculated. To investigate the tendency of the like molecules to self-associate the analyses are repeated by disregarding one of the two components. The self-aggregates of the disregarded component thus turn into large empty voids, which are easily detectable in VP analysis. The obtained results reveal that both molecules show self-association, but this behavior is considerably stronger among the acetone than among the methanol molecules. The strongest self-association of the acetone and methanol molecules is found in their mole fraction ranges of 02-0.5 and 0.5-0.6, respectively. The caging effect around the methanol molecules is found to be stronger than around acetones. Finally, the local environment of the acetone molecules turns out to be more spherical than that of the methanols, not only in the respective neat liquids, but also in their mixtures.