Lattice dynamics of RbI(001) surface studied by high-resolution medium energy ion scattering and molecular dynamics simulation

The anisotropy and correlations of the thermal vibrations of the RbI(0 0 1) surface were studied by high-resolution medium energy ion scattering (MEIS ) and molecular dynamics (MD) simulation. A new toroidal electrostatic anal yzer clearly resolved the two surface peaks from the top and second layer R b+ and I- ions making it possible to extract information about the thermal vibration amplitudes of the top and second layer ions and the correlation b etween them. In the present MD simulation, each ion is regarded as a point charge accompanied by a dipole moment interacting with other ions via a sem iempirical pair potential, We employed the dipole moments calculated by the shell model, giving surface relaxation and rumpling values consistent with our previously obtained result. The surface peaks observed for the [1 1 1] and [0 0 1] incidence were well reproduced by assuming the anisotropy and correlations derived by the MD simulations. (C) 2001 Elsevier Science B.V. All rights reserved.