Polarizability anisotropy dynamics in water-formamide mixtures

LADANYI, BRANKA M.; ELOLA, MARÍA DOLORES

Recent Progress in Computational Sciences and Engineering (2 vols) (Lecture Series on Computer and Computational Sciences)

VSP BV-C/O Brill Acad. Publ.

Lugar: Leiden; Año: 2006; p. 611 - 614

Abstract: We have carried out a molecular dynamics (MD) computer simulation study of the structure and dynamics of water-formamide mixtures at room temperature over the full range of compositions. Our studies of the structure have included the evaluation on intermolecular pair distribution functions, the tetrahedral order parameter, and numbers of hydrogen bonds per molecule. In the case of dynamics, the main focus has been on the collective polarizability anisotropy, but the mixtures were also characterized in terms of single-molecule translational and rotational mobilities and hydrogen bond lifetimes. Our studies indicate that water molecules are incorporated into the formamide hydrogen bond network. Translational diffusion coefficients and single-molecule rotational relaxation rates decrease with increasing formamide mole fraction. Since water molecules have a much smaller polarizability anisotropy than do formamide molecules, the collective polarizability anisotropy response is dominated by formamide collective orientational relaxation. Except at very low formamide mole fractions, water contributes mainly through its effects on formamide dynamics and to a lesser extent trhough the water-formamide interaction-induced polarizability.