High-Resolution Calculations on Atom-Surface Scattering: Method and Comparison with Experiment for Ne/LiF

Calculated scattering distributions for Ne on (001) LiF are compared with corresponding experimental distributions. For calculational purposes, the surface is effectively modeled by a monolayer of 3D harmonic oscillators representing F− ions. The atom-surface potential at close range is assumed to arise from two-body dispersion-exchange interactions which are represented by superposed Lennard-Jones (12, 6) model potentials. The foregoing potential is shown to be large with respect to that due to induced-dipole interaction. The long-range van der Waal's potential, for which the strength is independently specified, is taken to be one-dimensional in nature. The classical trajectory method combined with Monte Carlo distribution of surface impact coordinates and thermal states of gas/surface atoms is used to determine angular distributions of scattered beam intensity. Physical concepts underlying an efficient calculational algorithm required for high resolution scattering calculations are described. For a variety of incident beam conditions, including variation of beam ``temperature,'' angle of incidence, and azimuth of the plane of incidence, calculated angular positions of dominant intensity peaks in the scattered beam typically agree with experimental determinations to within 3°–5°. Predictions of high intensity ``ridge'' structure, which is quite different in form for the <010> and the <110> planes of incidence, are confirmed by experimental studies undertaken elsewhere. Calculated values of absolute scattering probability in the plane of incidence typically agree with prior experimental determinations to within 10%–15%. Statistical fluctuations in the calculated intensities (∼5%–10% of the calculated value) preclude a rigorous determination of whether or not the model reproduces all observed substructure on the high-intensity ridges. The parameters defining the semiempirical Ne/LiF potential used in the present study correspond to a heat of adsorption of ∼0.016 eV, and to a two-body range parameter of 3.9 Å. Means for determination of the potential parameters from a small part of the available experimental data and means for assessing the accuracy of these values are reported in a companion paper.