frustrated translations

 	Dear CCL'ers,
 	I would be very much obliged to anybody who could give me
 references on the following problem:
 	It is known that a molecule, after being adsorbed on a solid
 surface, loses its translational (and rotational - if it is not a
 monoatomic one) degrees of freedom. One of the translations is
 transformed into vibration against the adsorption site (and
 usually correlates very well with the adsorption energy). Two other
 translations are transformed to vibrations also, but the latter are
 the displacements in the plane of the surface. There are experimental
 measurements of these "frustrated translations" (e.g., by J.T.Yates,
 et el.). However, I failed to find any THEORETICAL SIMULATIONS of these
 	Any hint will be greatly appreciated. At the moment, it even
 doesn't matter for me, which molecules on which surface are adsorbed.
 	Summary is guaranteed.
 	Dr. Alexei Arbouznikov
         Ecole Nationale Superieure de Chimie,
 	Laboratoire de Materiaux Catalytiques et Catalyse en
 	Chimie Organique, UMR 5618 CNRS-ENSCM - Prof. F.Fajula,
         8, rue de l'Ecole Normale
         34296 Montpellier, Cedex 5
         Telephone: (33) 4-67-14-72-68
         Fax:   (33) 4-67-14-43-49
         E-mail: alexei ^at^