title: Ab initio molecular dynamics study of an aqueous NaCl solution under an electric field.
abstract: We report on an ab initio molecular dynamics study of an aqueous NaCl solution under the effect of static electric fields. We found that at low-to-moderate field intensity regimes chlorine ions have a greater mobility than sodium ions which, being a sort of "structure makers", are able to drag their own coordination shells. However, for field strengths exceeding 0.15 V Å(-1) the mobility of sodium ions overcomes that of chlorine ions as both types of ions do actually escape from their respective hydration cages. The presence of charged particles lowers the water dissociation threshold (i.e., the minimum field strength which induces a transfer of protons) from 0.35 V Å(-1) to 0.25 V Å(-1); moreover, a protonic current was also recorded at the estimated dissociation threshold of the solution. The behaviour of the current-voltage diagram of the protonic response to the external electric field is Ohmic as in pure water, with a resulting protonic conductivity of about 2.5 S cm(-1). This value is approximately one third of that estimated in pure water (7.8 S cm(-1)), which shows that the partial breaking of hydrogen bonds induced by the solvated ions hinders the migration of protonic defects. Finally, the conductivity of Na(+) and Cl(-) ions (0.2 S cm(-1)) is in fair agreement with the available experimental data for a solution molarity of 1.7 M.
authors: Institute of Biophysics - Czech Academy of Sciences, Královopolská 135, 61265 Brno, Czech Republic. giuseppe.cassone@impmc.upmc.fr.
authors: Giuseppe
authors: G
authors: Cassone
authors: Laboratoire Analyse et Modélisation pour la Biologie et l'Environment, UMR8587 (CHARMMMAT), Université d'Evry val d'Essone, Blvd. F. Mitterand, 91025 Evry, France. fabrizio.creazzo@pec.it.
authors: Fabrizio
authors: F
authors: Creazzo
authors: Università degli Studi di Messina, Dipartimento di Scienze Matematiche e Informatiche, Scienze Fisiche e Scienze della Terra, Contrada Papardo, 98166 Messina, Italy. paolo.giaquinta@unime.it.
authors: Paolo V
authors: PV
authors: Giaquinta
authors: CNR-IPCF, Viale Ferdinando Stagno d'Alcontres 37, 98158 Messina, Italy. saija@ipcf.cnr.it.
authors: Franz
authors: F
authors: Saija
authors: Sorbonne Universités, Université Pierre et Marie Curie Paris 06, Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, Unité Mixte de Recherche 7590, 75005 Paris, France. saitta@impmc.upmc.fr and CNRS, UMR 7590, IMPMC, 75005 Paris, France.
authors: A
authors: A
authors: Marco Saitta