1.1- Dichloroethane, bond distances

Recently, detailed molecular pictures of the interfacial structure on the time and distance scales of the ion-crossing event, as well as of ion transfer dynamics, have been provided by Benjamin s molecular dynamics computer simulations [71, 75, 128, 136]. The system studied [71, 75, 136] included 343 water molecules and 108 1,2-dichloroethane molecules, which were separately equilibrated in two liquid slabs, and then brought into contact to form a box about 4 nm long and of cross-section 2.17 nmx2.17 nm. In a previous study [128], the dynamics of ion transfer were studied in a system including 256 polar and 256 nonpolar diatomic molecules. Solvent-solvent and ion-solvent interactions were described with standard potential functions, comprising coulombic and Lennard-Jones 6-12 pairwise potentials for electrostatic and nonbonded interactions, respectively. While in the first study [128] the intramolecular bond vibration of both polar and nonpolar solvent molecules was modeled as a harmonic oscillator, the next studies [71,75,136] used a more advanced model [137] for water and a four-atom model, with a united atom for each of two... 

With more complicated and more polar structures, such as 1,2-dichloroethane as a simple example, or such as a peptide as a more complicated example, electrostatics can become not only important, but of major importance in describing some of the properties of the molecule. There is at present no general agreement as to just how electrostatics is best treated. Often Coulomb s law is used, and point charges are placed at atomic nuclei, and allowed to interact. Another approximation is to place point dipoles in bonds, and allow those to interact via dipole-dipole interactions. At long distances, the interactions between four point charges or two point dipoles give the same result. However, at short distances. 

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