Sega M, Kantorovich S S, Holm C, Arnold A
Institut für Computergestützte Biologische Chemie, University of Vienna, Währinger Strasse 17, 1090 Vienna, Austria.
Faculty of Physics, University of Vienna, Boltzmanngasse 5, 1090 Vienna, Austria and Ural Federal University, Lenin av. 51, 620083 Ekaterinburg, Russia.
J Chem Phys. 2014 Jun 7;140(21):211101. doi: 10.1063/1.4880237.
In the late 1970s, Hubbard and Onsager predicted that adding salt to a polar solution would result in a reduced dielectric permittivity that arises from the unexpected tendency of solvent dipoles to align opposite to the applied field. Here we develop a novel non-equilibrium molecular dynamics simulation approach to determine this decrement accurately. Using a thermodynamic consistent all-atom force field we show that for an aqueous solution containing sodium chloride around 4.8 mol/l, this effect accounts for 12% of the total dielectric permittivity. The dielectric decrement can be strikingly different if a less accurate force field for the ions is used. Using the widespread GROMOS parameters, we observe in fact an increment of the dielectric permittivity rather than a decrement, caused by ion pairing and introduced by a too low dispersion force.
