Molecular dynamics simulation of the free surface of liquid formamide

Oberbrodhage, J.; Morgner, Harald; Tapia, O.; Siegbahn, Hans

doi:10.1002/(sici)1097-461x(1997)63:6<1123::aid-qua5>3.0.co;2-z

Cited by 13 publications

(5 citation statements)

References 7 publications

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“…For formamide (unlike, e.g., methanol), the surface orientation is rather weak, with preference of the HCO group to point toward the vapor phase. 34 Similar orientation was also found in experiments by means of MIES 35 and ARISS. 36 A direct comparison of the ion scattering experiments and the simulation has to take into account the differences in the methods.…”

Section: Discussionsupporting

confidence: 82%

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Anions of Alkali Halide Salts at Surfaces of Formamide Solutions: Concentration Depth Profiles and Surface Topography

et al. 2007

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Previous computer simulations and surface-selective spectroscopic experiments indicated non-monotonic concentration depth profiles for soft inorganic ions (such as iodide) at the air/water interface while this surface effect was strongly quenched in methanol. Here, we investigate by means of neutral impact collision ion scattering spectroscopy and molecular dynamics simulations the surface propensity of anions of alkali halide iodide salts in formamide. By combination of experiments and calculations, we extract both the ion concentration depth profiles at the interface and the local solvent topography around the ions in or near the topmost layer of the liquid. We show that formamide, as a nonaqueous polar solvent containing no hydrophobic groups, exhibits an enhanced surface coverage of soft inorganic ions like iodide and that the ions are located in the outermost layer in valleylike structures. The non-monotonic interfacial concentration profile and surface propensity of iodide in formamide is quantified and compared to that in water.

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Section: Discussionsupporting

confidence: 82%

“…The simulations are also capable to analyze the orientation of solute molecules in the interfacial layer. For formamide (unlike, e.g., methanol), the surface orientation is rather weak, with preference of the HCO group to point toward the vapor phase . Similar orientation was also found in experiments by means of MIES and ARISS …”

Section: Discussionsupporting

confidence: 76%

Anions of Alkali Halide Salts at Surfaces of Formamide Solutions: Concentration Depth Profiles and Surface Topography

et al. 2007

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“…Our results indicate that these modes are somehow related to fluctuating intermolecular structure of the solvent adjacent to the hydrophobic-like area of the probe's surface (i.e., area that is free of probe−solvent H-bonds). Interestingly, molecules of branched H-bonding solvents (e.g., water and formamide) exhibit strongly anisotropic packing at hydrophobic and liquid/air interfaces in order to minimize the loss of H-bonds they would have in the bulk, − while nonanomalous solvents (e.g., methanol) exhibit qualitatively different interfacial organization . Thus, we cannot rule out that similar packing at the probe's surface may create a spatial correlator of polarization fluctuations which is not only different from that of nonanomalous solvents but also has a new superficial pattern of polarization fluctuations near the probe.…”

Section: Discussionmentioning

confidence: 99%

Anomalous Microscopic Dielectric Response of Dipolar Solvents and Water

Mertz

2004

J. Phys. Chem. A

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This paper reports measurements of static microscopic dielectric response of several dipolar solvents to charge redistribution in a fluorescent probe. Contrary to recent predictions of dielectric theories and computer simulations of bulk liquids, the observed dielectric response of most solvents conforms to the macroscopic continuum description even at atomic distances, as if these solvents had no spatial intermolecular structure. Such conformance is observed for several probes when the contribution of specific probe-solvent interactions to the response is negligible. However, water, formamide, and glycerol exhibit anomalous responses even though such a probe is used. We discuss a possible reason for the macroscopic-like behavior and a connection between the anomaly and fluctuating structures formed by anomalous solvents near the hydrophobic surface of the probe.

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“…For formamide, ARISS indicates either random orientation of molecules or a preferred orientation of the planar molecules lying “flat” on the surface. Existing MIES data and simulation results led to the conclusion that a preferential orientation of the formamide molecules exists, with the axis of the molecule tilted at a small angle to the surface. For benzylalcohol, a depletion of oxygen (due only to the hydroxyl group) was seen at the top surface layers, followed by an excess at around 4–5 Å. Andersson compared the oxygen concentration depth profile from the ARISS experiment to those obtained in simulations performed by Dietter and Morgner (see Figure ).…”

Section: Structure Of Pure Liquidsmentioning

confidence: 99%