An energy dispersive x-ray scattering and molecular dynamics study of liquid dimethyl carbonate

Abstract

In this work, we report on the first x-ray diffraction study on liquid dimethyl carbonate. Diffraction spectra were collected with an energy-dispersive instrument, whose wide Q-range allows the structure determination of weakly ordered systems (such as liquids). The structural correlation in this liquid ranges up to about 20 A. The observed patterns are interpreted with a structural model derived from classical molecular dynamics simulations. The simulations were run using OPLS force field, only slightly modified to restrain bond distances to the experimental values. The model structure function and radial distribution functions, averaged among the productive trajectory frames, are in very good agreement with the corresponding experimental ones. Molecular dynamics results show that the deviations from C(2v) cis-cis structure, predicted by ab initio calculations and observed by electron diffraction in the gas phase, are small. By analyzing the intra- and intermolecular pair distribution functions, it was possible to assign the peaks of the experimental radial distribution function to specific structural correlations, and to compute the different average intermolecular coordination numbers. The intermolecular methyl-carbonyl oxygen distance is thoroughly discussed to assess the presence of weak C-H...O hydrogen bonds.

Does High Pressure Induce Structural Reorganization in Linear Alcohols? A Computational Answer

“…[29] The compressibility constants for all the n-alcohols were taken from the literature. [30] The trajectories obtained were analyzed by using our in-house software and implementing the formulae described elsewhere [42] to obtain the structure function, by using the TRAVIS software [43] for miscellaneous properties and with g_rdf and g_clustsize (from the Gromacs [44] package) to obtain pair-distribution functions and perform cluster analysis, respectively.T he quality of the simulations was checked by considering three observables, that is, the density,t he structure function, and the diffusionc oefficient. The agreement between computed and experimental values for all data is excellent, as can be seen in Table 3a nd Figure 1.…”

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