Structure and dynamics of acetonitrile: Molecular simulation and neutron scattering

The Effect of Electric Fields on the Structure of Water/Acetonitrile Mixtures

“…The CDF, g CDF (r, θ), has a maximum at θ = 180°and r ∼ 0.37 nm, corresponding to configurations where the closest neighbors are at a distance of around 0.37 nm and the mutual orientation of CCN molecules is antiparallel. Earlier studies of pure CCN liquids 10,23 have reported a second peak suggesting an additional preference for perpendicular orientations with head-tail orientation. This peak is absent in our simulations of CCN/water mixtures.…”

“…As discussed in the introduction, experimental as well as computational studies suggest that neighboring CCN molecules have a tendency to adopt an antiparallel orientation, regardless of whether they are in a pure or solvated state. 10,[21][22][23]26,32 We use the combined distribution function (CDF) of angular and radial correlations to gain insight into the mutual orientation of the CCN molecules and how the distance between their center of masses affects these orientations, see Eq. 2 in Methods section.…”

“…For these reasons, CCN liquids and aqueous CCN solutions have been studied intensely for many decades 1 by experiments (e.g. NMR, spectroscopy, X-ray scattering), [2][3][4][5][6][7][8][9][10] theory, [11][12][13] and simulations, 5,8,10,[14][15][16][17][18][19][20][21][22][23][24][25][26][27] and a number of force fields have been proposed that are specifically optimized for CCN. [28][29][30][31][32][33][34][35] Among others, these studies have revealed a tendency of CCN to form clusters or small domains in water (so-called microheterogeneities) 9,17,21 in the concentration regime of 20%-75% CCN, 1,9 and pronounced orientational correlations between neighboring CCN molecules.…”

“…[28][29][30][31][32][33][34][35] Among others, these studies have revealed a tendency of CCN to form clusters or small domains in water (so-called microheterogeneities) 9,17,21 in the concentration regime of 20%-75% CCN, 1,9 and pronounced orientational correlations between neighboring CCN molecules. [10][11][12]21,23 The exact nature of correlation found in simulations somewhat depends on the force field: Earlier studies reported the formation of head-to-head dimers, 11,12 whereas more recent studies suggested a preference for antiparallel orientations and head-tail orientations where two neighbor CCN are perpendicular to each other. 10,21,23 Also, the hydrogen bond distribution in water/ CCN mixtures has been studied by various authors.…”

“…[10][11][12]21,23 The exact nature of correlation found in simulations somewhat depends on the force field: Earlier studies reported the formation of head-to-head dimers, 11,12 whereas more recent studies suggested a preference for antiparallel orientations and head-tail orientations where two neighbor CCN are perpendicular to each other. 10,21,23 Also, the hydrogen bond distribution in water/ CCN mixtures has been studied by various authors. 4,5,15,36 Since CCN is aprotic, such studies give insight into the connectivity of water in water/CCN mixtures, which should have an impact on the proton transport in these fluids.…”