Nazmutdinov, Renat R.; Spohr, Eckhard:

Partial charge transfer of the iodide ion near a water / metal interface

In: Journal of physical chemistry, Jg. 98 (1994) ; Nr. 23, S. 5956–5961
ISSN: 0022-3654, 0092-7325, 1541-5740
Zeitschriftenaufsatz / Fach: Chemie
Fakultät für Chemie
We have studied theoretically the partial charge transfer (PCT) between a hydrated iodide ion and a neighboring
platinum (100) surface by an approach that is a combination of quantum chemical cluster calculations, the
Newns-Anderson theory of chemisorption, and molecular dynamics simulations. The PCT from the bare ion
has been calculated from quantum chemical cluster calculations as a function of the distance from the metal
surface. The hydration energy of the undischarged iodide ion has been calculated by molecular dynamics
simulations at different ion-metal distances. Hydration and the surface dipole layer lead to a shift in the highest
occupied energy level of the adsorbate, which results in a significant reduction of the PCT compared with the
situation in vacuum. The equilibrium hydration energy of the ion as a function of its charge and as a function
of ion-metal distance was calculated on the basis of a Born-like approximation. The hydration energy of the
partially discharged ion is combined with the direct ion-surface interactions and the desorption energy of water
molecules to produce the total energy profile for iodide adsorption. Two minima separated by a small barrier
are observed, one corresponding to a contact-adsorbed, partially discharged, and partially dehydrated ion and
the other one corresponding to a fully hydrated iodide ion at larger distances.