Molecular Dynamics Simulations of a Silver Atom in Water: Evidence for a Dipolar Excitonic State
Riccardo
Spezia, Cédric Nicolas, and Anne Boutin
Laboratoire
de Chimie Physique, UMR 8000, CNRS, Université de Paris-Sud,
91405 Orsay Cedex, France
Rodolphe Vuilleumier
Laboratoire de
Physique Théorique des Liquides, UMR 7600, CNRS, Université
Pierre et Marie Curie, 4 Place Jussieu, 75252 Paris Cedex 05, France
(Received 23 May 2003; published 13 November 2003)
Abstract
The properties of a silver atom in bulk water were studied for the first time by molecular dynamics simulations using two complementary mixed quantum-classical approaches. The first one consists of treating by quantum mechanics one electron only, which interacts with a classical silver cation and solvent through one-electron pseudopotentials. The second one is Car-Parrinello molecular dynamics that treats all the valence electrons quantum-mechanically. Very good agreement is obtained between these two methods, and the calculated absorption spectrum of the solvated silver atom agrees very well with experimental data. Both simulations reveal that the silver atom is in the critical region for the appearance of a dipolar excitonic state and exhibits a dipole moment of ~2 D with large fluctuations of ±1 D. The structure of the solvation shell is also analyzed. ©2003 The American Physical Society